Consequences of Deforestation

By Rhett A. Butler
April 1, 2019

Rainforests around the world continue to disappear. But does it really matter? Why should people be concerned if some plants, animals, fungi, and microorganisms vanish? After all, tropical forests can be hot and humid, difficult to access, and filled with insects and elusive wildlife.

In reality, the issue is not just about the loss of individual species—though each plays a role in its ecosystem—but about the far-reaching consequences of rainforest destruction. By dismantling these vital ecosystems, we risk not only biodiversity loss but also disruptions to climate stability, local weather patterns, and essential ecological services. The decline of rainforests directly affects human well-being, including livelihoods, food security, and access to clean water.

While environmental degradation has not yet led to widespread ecosystem collapse in most areas, its cumulative effects are becoming increasingly evident. It is critical to examine the current impacts of forest loss and consider the long-term consequences. As natural systems degrade, human societies may face greater vulnerability to unexpected ecological shifts, including extreme weather events, water shortages, and declining agricultural productivity.

The most immediate effects of deforestation are felt at the local level, where the loss of tropical forests disrupts crucial ecological services. These ecosystems help regulate water cycles, prevent soil erosion, reduce flood risks, filter water, support fisheries, and enable pollination. Such functions are particularly vital for communities that rely directly on forests for sustenance and income. Additionally, deforestation reduces the availability of renewable resources such as timber, medicinal plants, nuts, fruits, and game, affecting both local economies and global markets.

Over the long term, tropical deforestation has far-reaching impacts on global climate and biodiversity. These shifts are harder to observe than local changes, as they unfold over extended timescales and often involve complex interactions. However, evidence increasingly suggests that large-scale forest loss contributes to shifts in regional rainfall patterns, temperature regulation, and carbon storage, affecting ecosystems and human societies worldwide.

Local and Regional Consequences of Deforestation

The most immediate consequences of deforestation are experienced at the local level. When forests are cleared, communities lose the benefits that these ecosystems provide, often without realizing their full value until they are gone. Forests help maintain clean water supplies, regulate rainfall, and mitigate the effects of extreme weather events. Acting as natural sponges, tropical rainforests absorb heavy rainfall, stabilize soils, and release water gradually, reducing the risks of both flooding and drought.

When forest cover is lost, rainfall runoff increases dramatically, leading to soil erosion and flash floods. During the rainy season, streams and rivers swell rapidly, often inundating downstream villages, cities, and agricultural fields. Conversely, in the dry season, deforested regions become more vulnerable to prolonged droughts. With fewer trees to retain moisture, rivers shrink, making navigation more difficult, disrupting irrigation systems, and threatening local food production and industrial activities.

Forests located on steep slopes, such as montane and watershed forests, play a particularly crucial role in regulating water flow and preventing landslides. Yet, these forests have been among the hardest hit by deforestation. During the 1980s, montane forests experienced some of the highest deforestation rates among tropical forests. (By the late 1990s and 2000s, upland forests began to recover in some regions, while lowland forests faced intensified pressure from agricultural expansion.)

Forests contribute significantly to local humidity through transpiration—the process by which plants release water through their leaves. This moisture plays a crucial role in sustaining regional rainfall patterns. In the central and western Amazon, for example, an estimated 50–80% of atmospheric moisture remains within the ecosystem’s water cycle. Water evaporates and transpires from the forest into the atmosphere, forming clouds that eventually return as precipitation. When forests are cleared, this cycle is disrupted, leading to reduced cloud formation and, ultimately, a decline in rainfall. As rainfall decreases, prolonged drought can take hold, transforming once-lush forests into arid landscapes.

This phenomenon is visible in multiple regions. Madagascar, for instance, has lost vast tracts of forest over generations due to clearing by fire, leaving much of the land barren and prone to desertification. River flows diminish, and less clean water reaches cities and agricultural areas. In West Africa, the decline in rainfall in interior regions has been partly attributed to excessive deforestation along the coast. Similarly, research in Australia suggests that without human influences—particularly large-scale agricultural burning—the dry outback might be a wetter and more hospitable environment. Vegetation change from forests that encourage rainfall to grasslands or shrublands can significantly alter precipitation patterns.

Colombia, once ranked second globally in freshwater reserves, fell to 24th place within just three decades due to extensive deforestation. Meanwhile, excessive forest loss around Kuala Lumpur, Malaysia, combined with dry conditions linked to El Niño, led to severe water shortages in 1998. That year, the city faced unprecedented water rationing and had to import water for the first time in its history.

There is growing concern that widespread deforestation could trigger a self-reinforcing cycle of declining rainfall and drying landscapes. This positive-feedback loop could accelerate regional desiccation, reducing remaining forest moisture and further stressing vegetation. If such changes continue unchecked, their impacts could extend beyond forested regions, affecting crucial agricultural zones and freshwater sources. At the 1998 global climate conference in Buenos Aires, British officials cited a study from the Institute of Ecology in Edinburgh warning that the Amazon rainforest could face near-total loss within 50 years due to shifts in rainfall patterns driven by climate change and land conversion.

As forests dry out, they become increasingly vulnerable to large-scale fires. This risk was starkly demonstrated during the 1997–1998 El Niño event, when millions of acres burned across Indonesia, Brazil, Colombia, Central America, Florida, and beyond. In 1998, the Woods Hole Research Center identified over 400,000 square kilometers of the Brazilian Amazon as highly fire-prone. The situation worsened in subsequent years, particularly in 2005 and 2010, when record droughts intensified the risk of wildfires across the region.

Soil Erosion and Its Effects

The loss of trees, which stabilize soil with their roots, leads to widespread erosion in tropical regions. Only a limited number of areas have naturally fertile soils, and once forests are cleared, heavy rains rapidly wash away topsoil. This depletion reduces agricultural productivity, forcing farmers to either rely on costly imported fertilizers or clear additional forested land, perpetuating the cycle of deforestation.

Costa Rica loses an estimated 860 million tons of topsoil each year, while Madagascar—often called the "Great Red Island" due to its iron-rich soils—experiences some of the highest erosion rates in the world. Soil loss there averages around 400 tons per hectare annually, turning rivers a striking red as sediment flows into the surrounding Indian Ocean. Astronauts have even described Madagascar from space as appearing to "bleed" into the sea, a stark visual reminder of the country’s severe environmental degradation. In agriculture-dependent economies, such rapid soil depletion threatens food security and livelihoods.

The acceleration of soil loss following deforestation can be dramatic. A study in Côte d'Ivoire found that forested slopes lost only 0.03 tons of soil per hectare per year. However, once converted to cultivated land, erosion increased to 90 tons per hectare annually, while bare slopes saw losses of 138 tons per hectare.

Heavy tropical rains further compound the problem by carrying loosened soil into creeks and rivers. This erosion disrupts waterways and causes widespread consequences. Hydroelectric projects and irrigation systems suffer from silt accumulation, reducing their efficiency. Industrial operations, which rely on stable water supplies, may be forced to suspend activities due to excessive sedimentation. Additionally, rising riverbeds from sediment buildup can intensify flooding and create sandbars that make navigation more difficult.

Erosion also threatens aquatic ecosystems. Increased sediment loads in rivers smother fish eggs, reducing hatch rates and impacting fisheries. When the suspended particles reach coastal waters, they make the water murky, harming coral reefs and disrupting marine life. The decline of coral reefs—often referred to as the rainforests of the sea due to their exceptional biodiversity—has alarmed scientists, as these ecosystems provide essential services, including coastal protection and fish nurseries. Additionally, mangrove forests, which serve as critical breeding grounds for many marine species, suffer from heavy siltation, further jeopardizing coastal fisheries.

Beyond harming marine life, deforestation-driven erosion can destabilize roads and highways, particularly in areas where infrastructure cuts through forested landscapes. Landslides and road washouts, triggered by soil loss, disrupt transportation and impose costly repairs.

For many developing countries, erosion carries enormous economic costs. The loss of infrastructure, declining fisheries, and reduced agricultural yields amount to tens of billions of dollars in damages annually. For example, in the late 1980s, the Indonesian island of Java lost an estimated 770 million metric tons of topsoil each year. This depletion was equivalent to the loss of 1.5 million tons of rice—enough to meet the food needs of 11.5 to 15 million people.

Environmental Refugees

Environmental degradation is increasingly forcing people to leave their homes, creating a growing population of "environmental refugees." These individuals are displaced due to factors such as deforestation, rising sea levels, desert expansion, and extreme weather events. According to Red Cross research, environmental disasters now displace more people globally than armed conflicts.

Impact of Deforestation – Species Loss, Extinction, and Disease

A healthy, intact forest has remarkable regenerative capacity. However, excessive hunting of wildlife in tropical rainforests can deplete key species essential for forest regeneration. In Central Africa, for instance, the decline of gorillas, chimpanzees, and elephants has disrupted seed dispersal processes, slowing the natural recovery of degraded forests.

Deforestation in the tropics also has cascading effects beyond these ecosystems. The loss of tropical habitat has been linked to declines in temperate species, particularly migratory birds that rely on tropical forests during the non-breeding season. North American migratory bird populations, which play a critical role in seed dispersal in temperate forests, declined by an estimated 1–3% annually from 1978 to 1988.

Emerging and Resurgent Tropical Diseases

The spread of tropical diseases, including emerging infectious diseases such as Ebola and Lassa fever, is an often-overlooked but serious consequence of deforestation. As human activity pushes deeper into rainforests—whether through logging, agriculture, or road construction—people come into contact with previously isolated microorganisms, some of which have the potential to cause severe illness. The disruption of forest ecosystems can displace or eliminate primary host species, increasing the likelihood that these pathogens spill over into human populations.

While no single pathogen has yet triggered a pandemic comparable to the devastation humans have inflicted on rainforest species, the possibility remains. In the meantime, many communities in deforested regions face an increased burden of mosquito-borne diseases such as dengue fever, Rift Valley fever, and malaria, as well as waterborne diseases like cholera.

Many emerging and re-emerging diseases are directly linked to land-use changes that bring humans into closer contact with disease vectors. For example, malaria and schistosomiasis have become more prevalent due to the proliferation of artificial water sources such as dams, rice paddies, drainage ditches, irrigation canals, and puddles left behind by heavy machinery. Malaria transmission is particularly high in deforested and degraded areas, where stagnant water pools provide ideal breeding grounds for mosquitoes. By contrast, undisturbed forested areas tend to have fewer mosquito-friendly habitats, limiting disease transmission.

Malaria—estimated to infect 300 million people globally each year and cause 1–2 million deaths—poses a severe threat to forest-dwelling Indigenous peoples, particularly uncontacted tribes who lack immunity and access to antimalarial treatment. In the 1990s, malaria was cited as a factor in the deaths of an estimated 20% of the Yanomami people in Brazil and Venezuela. The emergence of drug-resistant malaria strains is further complicating efforts to control the disease, even in regions where it was once thought to be under control. Climate models suggest that rising global temperatures could expand the range of malaria-carrying mosquitoes, potentially increasing the disease’s reach.

The spread of infectious diseases in tropical regions does not remain confined to those areas. Due to global travel and trade, pathogens can quickly reach distant parts of the world. For instance, a doctor in Central Africa exposed to the Ebola virus could board a plane and arrive in London within 10 hours, potentially exposing passengers and spreading the virus to new populations. Airport hubs facilitate rapid disease transmission, allowing outbreaks to spread across continents before symptoms are even recognized.

According to the U.S. Centers for Disease Control and Prevention (CDC), deaths from infectious diseases have been rising. Infectious diseases remain the leading cause of death globally and the third leading cause of death in the United States. Throughout history, infectious diseases have played a significant role in human mortality. During World War I, at least one-third of all deaths were attributed to disease, primarily influenza. The 1918–1919 influenza pandemic killed an estimated 20 to 100 million people worldwide—far more than the total military and civilian casualties of the war itself.

Destruction of Renewable Resources

Deforestation not only strips a country of its natural wealth but also replaces productive forestlands with degraded landscapes that provide limited economic value. Tropical forests support a range of renewable resources that can contribute significantly to national economies when managed sustainably.

In theory, logging can be a sustainable industry, providing ongoing revenue while maintaining the forest resource base—particularly in secondary forests and plantations. However, in practice, most rainforest logging is not managed sustainably, leading to long-term economic losses for tropical countries. Overexploitation has diminished forestry’s importance in many former wood-exporting nations, particularly in Southeast Asia and West Africa. While some governments have implemented logging restrictions, others continue to struggle with illegal operations. The World Bank estimates that illegal logging costs governments approximately US$5 billion annually in lost revenues, with overall economic losses to timber-producing countries amounting to an additional US$10 billion per year.

Beyond logging, one of the most valuable "renewable resources" that tropical forests provide is ecotourism. This industry generates tens of billions of dollars annually for tropical nations. However, deforestation undermines ecotourism—few travelers are drawn to polluted rivers, barren landscapes, or remnants of once-thriving wildlife populations. The degradation of forests directly reduces a country’s ability to capitalize on nature-based tourism.

Forest products remain crucial to the economies of many developing nations. According to the UN Food and Agriculture Organization (FAO), reported income from forest products exceeded $120 billion in the late 2000s. About 20% of this value came from secondary forest products, though actual figures are likely much higher when accounting for informal use by local communities. Many forest-dependent people rely on timber for construction and collect nuts, fruits, and other non-timber products for subsistence and trade. Short-term deforestation-driven economic gains often lead to long-term economic hardship, as the destruction of forests eliminates not only valuable ecological services but also potential future revenues from sustainable forest management.

The decline of tropical hardwood exports is a clear example of this trend. Since 1980, Malaysia has experienced a 60% drop in log exports, while the Philippines—once a major exporter of tropical logs in the early 1980s—has seen its log export industry nearly disappear. In both cases, unsustainable harvesting practices have severely reduced the availability of commercial timber.

Beyond timber, tropical forests provide numerous high-value renewable resources, including Brazil nuts from the Amazon, durian fruit from Southeast Asia, and resin from Damar trees in Sumatra. A study by CIFOR found that non-timber forest products contribute up to 20% of rural incomes, often serving as the only means for forest-dependent communities to participate in the cash economy. Many of these products rely on the integrity of the rainforest ecosystem, meaning deforestation threatens not just the resources themselves, but also the livelihoods of those who depend on them.

Human-Wildlife Conflict

As forests shrink, wildlife is increasingly forced to venture beyond its natural habitat in search of food and space, bringing animals into closer contact with human settlements. This often leads to conflict, as species such as elephants, venomous snakes, and big cats enter agricultural lands and populated areas. Fatal encounters with wildlife tend to occur in and around degraded forest areas where natural food sources have diminished.

Human-elephant conflict is particularly common in Asia. Conservationists and authorities have worked on strategies to mitigate these conflicts—such as creating buffer zones and using deterrent methods—while ensuring the safety of both people and elephants. However, many farmers still resort to killing elephants that damage their crops, and in some cases, these animals are opportunistically targeted for their ivory.

In Indonesia, a series of tiger attacks on illegal loggers made headlines in 2009. The loggers were killed while extracting timber from protected rainforests in Sumatra, highlighting the risks of encroaching into critical wildlife habitat.

While predator attacks on livestock can be a concern, research has shown that estimates of livestock losses due to predation are often exaggerated—especially in cases where compensation schemes are in place. In reality, other factors such as disease and poor husbandry practices frequently account for a significant portion of livestock losses.

Climatic Role of Forests

Tropical rainforests are integral to the regulation of both local and global climate. These forests influence weather patterns through their role in rainfall production and atmospheric gas exchange. The Amazon alone generates 50–80% of its own rainfall through transpiration. Deforestation disrupts this process, altering the reflectivity of Earth's surface, shifting wind and ocean current patterns, and affecting precipitation distribution. Continued forest loss could contribute to more extreme and unpredictable weather patterns worldwide.

Forests and Climate Regulation

As previously discussed, tropical rainforests play a crucial role in regulating local climates through their interaction with the water cycle. Beyond this, forests significantly impact global weather patterns. Vegetation influences Earth's "surface albedo," or reflectivity, by absorbing more heat than bare soil. This process warms the air and carries moisture from trees into the atmosphere, where it condenses and falls as rain. In other words, forests help cool local climates while also driving precipitation. Conversely, deforestation reduces heat absorption, leading to lower atmospheric moisture levels and decreased rainfall.

Additionally, deforestation-related fires release large quantities of aerosols—tiny airborne particles—into the atmosphere. Aerosols can influence temperature in various ways depending on their composition, but high concentrations of smoke and particulate matter have been shown to disrupt rainfall patterns. NASA research suggests that in areas with dense smoke, "cloud droplets form around the aerosol particles but may never grow large enough to fall as rain." This feedback loop exacerbates drought conditions and increases the likelihood of further fires.

Over time, these changes contribute to long-term declines in regional rainfall.

Tropical deforestation also affects weather in distant parts of the world. A 2005 NASA study found that forest loss in the Amazon influences precipitation as far away as Mexico, Texas, and the Gulf of Mexico. Similarly, deforestation in Central Africa has been linked to shifts in rainfall patterns across the U.S. Midwest, while forest loss in Southeast Asia has been associated with climatic changes in China and the Balkan Peninsula.

In 2007, two Russian physicists proposed a new theory known as the "biotic pump," suggesting that forests actively generate the winds that bring rainfall to landmasses. The theory remains controversial, but it highlights the complex interactions between forests and climate.

Atmospheric Role of Forests: Rainforests and Climate Change

Rainforests play a critical role in regulating atmospheric carbon levels by sequestering carbon through photosynthesis. However, when forests are burned, degraded, or cleared, they release significant amounts of carbon dioxide and other greenhouse gases, including nitrous oxide and methane. The clearing and burning of tropical forests and peatlands contribute more than a billion metric tons of carbon (3.7 billion tons of carbon dioxide) to the atmosphere each year—accounting for more than 10% of human-induced carbon emissions.

The buildup of carbon dioxide and other greenhouse gases in the atmosphere is known as the "greenhouse effect." This accumulation alters Earth's radiative balance, trapping heat and contributing to global warming. Greenhouse gases like carbon dioxide allow shortwave solar radiation to pass through but absorb long-wave infrared radiation emitted by Earth's surface, preventing heat from escaping.

Fossil fuel combustion is the largest anthropogenic contributor to carbon emissions, accounting for over 85% of emissions. Industrial activities such as cement, steel, and aluminum production contribute an additional share. Preindustrial carbon dioxide levels were around 280 parts per million (ppm), but today they exceed 400 ppm—a 43% increase. Climate projections suggest that reaching 450 ppm—expected by 2050—could lead to a 1.8–3°C (3.2–5.4°F) rise in global temperatures.

The long-term effects of climate change remain a subject of scientific debate, but evidence suggests that it could contribute to rising sea levels, increased storm intensity, shifting ocean currents, and more frequent extreme weather events. Some scientists predict that global warming could lead to sharp temperature increases, followed by long-term climatic shifts. However, many uncertainties remain about the precise trajectory of climate change.

In 1995, the Intergovernmental Panel on Climate Change (IPCC) concluded that "the balance of evidence suggests a discernible human influence on global climate." Key indicators include rising global temperatures, retreating glaciers, changes in polar ice sheets, and a record number of extreme weather events. Data from the National Oceanic and Atmospheric Administration (NOAA) indicates that 1998 was the warmest year on record at the time, with subsequent years—including 2005 and 2010—continuing the trend. The IPCC projects that atmospheric carbon dioxide levels could reach 450–550 ppm by mid-century, with widespread implications for ecosystems, human societies, and weather patterns worldwide.

Rising Sea Levels

The projected rise in sea level due to ocean expansion and ice melt varies depending on the extent of global warming. However, estimates suggest that if greenhouse gas emissions continue at current rates, sea levels could rise by 10 to 20 inches (25–50 cm) within the next century. While this may seem like a modest increase, the impact on human communities and natural systems could be profound. Higher sea levels would exacerbate the effects of tides, storm surges, and hurricanes, as demonstrated by the devastation caused by Hurricane Katrina in 2005. Low-lying island nations such as the Maldives and various South Pacific states face existential threats from rising waters.

The ocean is a critical resource for humanity, and many of the world’s largest cities are located along coastlines, benefiting from trade, fishing, and tourism. Rising sea levels threaten these urban areas, leading to coastal flooding, disruption of sewage and transportation infrastructure, and inundation of agricultural lands. Coastal ecosystems—such as river deltas, wetlands, and mangrove forests—provide vital services, including flood mitigation and habitat for diverse species. Although sea levels have fluctuated in Earth’s history, modern human settlements are far more dependent on existing shorelines. Even a small rise in sea level could have significant social, economic, and environmental consequences, underscoring the fact that global warming is as much a social issue as it is an environmental one.

Changes in Ecosystems

Climate change is expected to cause significant shifts in species distribution and ecosystem composition, though the extent of these changes remains an area of active scientific research. Models suggest that coral reefs, highly sensitive to ocean temperature and acidity, could decline drastically over the next 50 years. Many marine organisms at the base of the oceanic food chain may also be affected, with cascading effects throughout marine ecosystems. On land, melting permafrost in high-latitude regions may give way to forest expansion, while agricultural zones may shift poleward. In the Amazon, increasing temperatures and prolonged dry seasons could transform large portions of rainforest into savanna. Meanwhile, in Africa, climate change could disrupt seasonal weather patterns, reducing rainfall in some areas while intensifying precipitation in the historically drought-prone Sahel region.

The good news is that some carbon emissions can be offset through reforestation, as trees absorb carbon dioxide via photosynthesis. Tropical forests, in particular, have significant potential for carbon sequestration due to their rapid growth rates and high biomass density. Reforesting an area of 3.9 million square miles (10 million square km) could sequester an estimated 3.7 to 5.5 billion metric tons of carbon dioxide over the next 50 to 100 years.

Several tree-planting initiatives have been launched worldwide to mitigate carbon emissions. One early effort was a coalition of developing countries at the 2005 UN climate conference in Montreal, which proposed compensating forest conservation through carbon payments. This concept later evolved into the Reducing Emissions from Deforestation and Forest Degradation (REDD+) mechanism, which aims to mobilize billions of dollars in carbon finance to support tropical forest protection. [Latest news on avoided deforestation, carbon finance, and REDD.]

While programs like REDD+ provide financial incentives for forest conservation, the challenge remains that even if carbon emissions were halted today, there would be a lag of approximately 50 years before climate stabilization due to ocean thermal inertia—oceans’ ability to store heat. This means the full effects of past emissions are not yet fully realized.

Lungs of the Earth

The role of rainforests in global oxygen production is often exaggerated—microorganisms in the world’s oceans produce more oxygen than terrestrial forests. However, tropical rainforests do contribute significantly to oxygen generation through photosynthesis. Some scientists estimate that rainforests are responsible for around 20% of the planet’s oxygen production, although this is largely offset by plant respiration, which consumes oxygen at night.

A more accurate way to describe rainforests as the "lungs of the Earth" is in their function as carbon sinks, helping to regulate atmospheric carbon dioxide levels. Additionally, their role in maintaining local humidity and regional rainfall patterns is critical to sustaining global ecosystems.

Deforestation and Extinction

The most lasting consequence of deforestation is the mass extinction of species that sustain Earth's biodiversity. While mass extinctions have occurred in the past, none have happened as rapidly or been so directly driven by a single species. The current extinction rate is estimated to be 1,000 to 10,000 times higher than the natural background extinction rate of 1–10 species per year.

So far, there is limited evidence of the mass extinctions predicted by the species-area curve (see chart below). However, many biologists argue that extinction, like climate change, has a time lag. The loss of species due to past deforestation may not yet be fully apparent. Ward (1997) introduced the concept of "extinction debt," referring to the delayed extinction of species long after habitat destruction:

• Decades or even centuries after habitat disturbance, extinctions caused by the disruption may still be occurring.
• This phenomenon is often underestimated—forests may be clear-cut, and the immediate loss of species may seem low, but extinctions continue long after the initial disturbance.
• By overexploiting wildlife, humans may assume they are "saving" a species when population numbers stabilize at low levels, but in reality, an extinction debt remains, eventually leading to species loss.

For example, the loss of key pollinators may not immediately impact long-lived tree species, but their eventual decline is inevitable. A study on West African primates found that historic deforestation had created an extinction debt, with over 30% of primate species at risk due to past habitat destruction. This suggests that simply protecting remaining forests may not be enough to prevent extinctions resulting from historical deforestation.

The process of extinction is highly complex, involving numerous interacting factors. Some extinctions, particularly of small or isolated populations, are better understood. Since MacArthur and Wilson’s 1967 work, The Theory of Island Biogeography, ecologists have extensively modeled how population size and habitat area affect species survival.

Populations naturally fluctuate due to environmental and genetic factors, but for isolated populations or critically endangered species, these fluctuations can push them below the minimum viable population (MVP)—the threshold below which recovery becomes unlikely. Three major forces contribute to species decline once MVP is reached:

Demographic Stochasticity

This refers to random fluctuations in birth and death rates within a population. Small populations are particularly vulnerable to such randomness. Species with low reproductive rates (e.g., primates, birds of prey, elephants) take longer to recover from population declines. Social species that rely on group dynamics, such as herding mammals or pack predators, may also suffer when numbers drop too low to sustain cooperative behaviors. For example, large carnivores that range widely may struggle to find mates when populations fall below a critical density.

Environmental Stochasticity

This includes unpredictable changes in weather, food supply, and natural disasters like fires, floods, and droughts. For species confined to small areas, a single severe drought or extreme weather event can wipe out an entire population.

Reduced Genetic Diversity

Small populations have limited genetic variation, making them more susceptible to disease, reduced adaptability, and inbreeding depression. Without gene flow from other populations, genetic drift can further erode genetic diversity, pushing species toward extinction.

The combination of these factors creates an "extinction vortex," where declining populations become increasingly vulnerable to further losses. See the extinction vortex model for a detailed explanation.

Some ecologists suggest that species population dynamics may be governed by chaotic properties, making extinction patterns difficult to predict due to the complexity of ecosystems.

Climate Change and Extinction

Tropical species are not only threatened by habitat destruction but also by climate change. Even species within protected reserves may be at risk due to rising temperatures, shifting precipitation patterns, and extreme weather events. Many tropical organisms are highly specialized for stable temperature and humidity conditions and may struggle to adapt to even minor climate shifts.

For example, cloud forests rely on persistent moisture, and even a slight increase in temperature could lift cloud layers beyond the reach of forest vegetation, causing ecosystem collapse. Similarly, extreme weather fluctuations, such as those associated with El Niño and La Niña, can disrupt wildlife populations. If extreme events become more frequent, species may not have enough time to recover between disturbances.

Climate change also facilitates the spread of diseases among wildlife. In Hawaii, rising temperatures may allow mosquitoes carrying avian malaria and bird pox to reach high-elevation forests, threatening endemic bird species that have never been exposed to these pathogens.

Barriers to Species Migration

In the past, species survived climate shifts by migrating to more suitable habitats. However, modern human development—highways, cities, farms, and plantations—has severely restricted migration pathways. Without natural corridors, many species may be unable to relocate as climate zones shift, increasing their risk of extinction.

A possible factor in the global decline of amphibians is climate change, which, combined with increased UV-B radiation, may have weakened their immune systems and made them more susceptible to fungal infections. The chytrid fungus, which has been detected in dying frogs worldwide, has been linked to climate-related stressors.

Historical Extinctions and the Role of Humans

Climate change may have contributed to the extinction of North America’s megafauna at the end of the last Ice Age. Giant sloths, mammoths, sabertooth cats, and other large mammals likely faced habitat fragmentation due to warming climates. However, some scientists argue that human hunting played a decisive role. The Moisimann and Martin (1975) model, later refined by Whittington and Dyke (1989), suggests that hunting even a small percentage of a species' population each year could drive it to extinction within a few centuries.

Today, we are witnessing a similar scenario, but with both climate change and habitat destruction driven by human activities.

The Domino Effect of Extinction

The interconnectedness of species means that the loss of one can trigger cascading effects throughout an ecosystem. David Quammen (1981) explains:

• Each plant species supports 10–30 species of dependent animals.
• Eliminating a single insect species could wipe out the only pollinator for a flowering plant.
• The disappearance of that plant could lead to the extinction of 20+ insect species that rely on it for food.
• Some of those insects may have played a key role in controlling agricultural pests—without them, pests could proliferate, damaging entire forests.

The intricate web of life in rainforests makes it nearly impossible to predict the full consequences of species loss.

Loss of Genetic Diversity

Beyond the intrinsic value of biodiversity, the extinction of species also means the loss of irreplaceable genetic resources. These genetic codes—shaped by millions of years of evolution—hold potential applications in medicine, agriculture, and biotechnology. Each extinct species represents a vanished genetic blueprint that could have provided new pharmaceuticals, disease-resistant crops, or other benefits to humanity.

As species disappear, the world loses not only its biological richness but also opportunities for scientific discovery and ecological resilience.

Estimates of annual species loss vary widely, as shown in this table.

REVIEW QUESTIONS

Review questions - Part I

• Why are rainforests important?
• Why should rainforests be protected?

Review questions - Part II

• How do rainforests help moderate flood and drought cycles?

Review questions - Part III

• Why do rainforests help prevent erosion?
• Why is erosion a problem?
• What are environmental refugees?

Review questions - Part IV

• How is deforestation linked to the emergence of disease?

Review questions - Part V

• Why are secondary forest products important?

Review questions - Part VI

• Why does local rainfall decline with deforestation?

Review questions - Part VII

• How does deforestation affect global warming?
• Why are rainforests called "the lungs of the world"?

Review questions - Part VIII

• Why is there a "lag time" for species extinction?
• Why do small populations have a lower probability of survival?
• How might climate change impact global biodiversity?
• Why are frogs dying around the world?

CITATIONS

Citations - Part I

Citations - Part II

• N. Myers in "Deforestation Rates in Tropical Forests and Their Climactic Implications," Friends of the Earth, London, 1989 estimates that the tropical deforestation rate increased by 90% during the 1980s.
• The "Estimated Annual Rates of Deforestation" chart is derived from Orr, D.W., Earth in Mind: On Education, Environment, and the Human Prospect, Washington, D.C.: Island Press, 1994; State of the World's Forests 1997 (SOFO) published by the United Nations Food and Agriculture Organization (FAO); and N. Myers in "Deforestation Rates in Tropical Forests and Their Climactic Implications," Friends of the Earth, London, 1989.
• The U.N. FAO (State of the World's Forest 1997 (SOFO)) provides statistics revealing the high deforestation rates of tropical montane forest during then 1980s.
• According to Salati, E. and Nobre, C.A ("Possible climatic impacts of tropical deforestation," in Tropical Forests and Climate, ed N. Myers., Dordrecht: Kluwer Academic Publishers, 1992) 50-80% of the moisture in the central and western Amazon is recycled.
• Myers, N. in "The world's forests and their ecosystem services," in Nature's Services: Societal Dependence on Natural Ecosystems, ed G.C. Daily, Washington D.C.: Island Press, 1997 explains how moisture is transpired by plants and evaporated back into the atmosphere to form rain clouds.
• A. Gioda reviews the importance of water throughout history in "A Short History of Water" Nature & Resources, Vol. 35, No. 1, Jan-Mar 1999.
• Szollosi-Nagy, A., Najlis, P., and Bjorklund, G breadown the availability of global freshwater resources in "Assessing the world's freshwater resources," Nature & Resources, Vol. 34, No. 1, Jan-Mar 1998.
• Albor, T. reported on severe flooding in the Philippines resulting from deforestation ("Illegal Logging blamed for Philippine Flood Toll," Christian Science Monitor 11/12/91).
• Pearce attributes declining rainfall in interior West African countries to coastal forest loss (Pearce, F., "Lost Forests Leave West Africa Dry," The New Scientist 1-18-97.).
• Vegetation change caused by ancient human agricultural fires may have impacted precipitation patterns in the Austalian outback according to Cowen, R. ("If You Don't Spare the Tree, You May Spoil More Than the Jungle," Christian Science Monitor. 1/13/98) and Johnson, B.J. et aL. ("65,000 years of vegetational change in central Australia and the Australian summer monsoon," Science Vol. 284, No 5417 (1150-1152), 14-May-1999).
• In his article "Escaping Nature's Wrath" in the Chronicle Foreign Service (1998), P. Grunson discusses the role of environmental degradation on damage inflicted by Hurricane Mitch.
• In his book, Ultimate Security: The Environmental Basis of Political Stability (Washington, D.C.: Island Press. 1996), Norman Myers discusses the importance of environmental stability in maintaining social and policial stability. He indicates that shrinking water supplies will have important political raminfications in the near future.
• The decline of Colombia's freshwater resources is mentioned in Inter Press Service (IPS), "Environment-Colombia: Garbage, Guerrillas and Animal Smugglers" 1/7/98.
• N. Myers brings up the concern that widespread deforestation could trigger a positive-feedback process of increasing dessication for neighboring forest cover in "The world's forests and their ecosystem services" in Nature's Services: Societal Dependence on Natural Ecosystems, ed G.C. Daily, Washington D.C.: Island Press, 1997.
• At the 1998 global climate treaty conference in Buenos Aires, the Nautral Environment Research Coucil of the UK released a study forcasting the conversion of 2.8 million square kilometers of the Amazon rainforest to desert resulting from global climate change. This dire projection has been considered too extreme by many climate researchers since its release. Nevertheless the story was picked up by McCarthy, M. in "Amazon forest 'will be dead in 50 years'" The Independent. 11/11/98.
• In its RisQue98 (Risco de Queimada, or "Risk of Burning" in Amazonia - 1998), the Woods Hole Research Center assessed the risk of forest fires and agricultural burning in Brazilian Amazonia for the second half of 1998 and found that more than 400,000 square kilometers were vulnerable.

Citations - Part III

• J. Omang ("In the Tropics, still rolling back the rain forest primeval," Smithsonian (March 1987) reported the rate of erosion in Costa Rica.
• Photograhper Frans Lanting made the comment that from space it looks as if Madagascar is bleeding to death from rampant erosion in A World Out of Time-Madagascar, New York: Aperture Foundation, Inc., 1990.
• UNESCO/UNEP/FAO, in Tropical Forest Ecosystems, 1978 provides the erosion rates for different vegetation types in an Ivory Coast study.
• A discussion on the worst coral bleaching on record in 1998 can be found in Wilkinson et al., (Wilkinson, C., O. Linden, H. Cesar, G. Hodgson, J. Rubens, and A. E. Stong, "Ecological and socioeconomic impacts of 1998 coral bleaching in the Indian Ocean: an ENSO impact and a warning of future change?" Ambio, 1999) the U.S. Department of State's "Coral Bleaching, Coral Mortality, and Global Climate Change," Bureau of Oceans and International Environmental and Scientific Affairs U.S. Department of State, March 5, 1999; and Wilkinson, C. and Hodgson, G. ("Coral reefs and the 1997-1998 mass bleaching and mortality," Nature and Resources Vol. 5, No. 2, Apr-June 1999).
• Magrath and Areans (Magrath, W. and P. Arens., The costs of soil erosion on Java: a natural resource accounting approach, The World Bank, Washington, D.C., 1993) estimate the annual cost of erosion for Java in terms of rice production.

Citations - Part IV

• The decline in North American migratory birds over the 1978-1988 period is reported by the U.S. Fish and Wildlife Service in its Breeding Birds Survey 1990 and further detailed in Terborgh, J.W., Where Have All the Birds Gone? Essays on the Biology and Conservation of Birds that Migrate to the American Tropics, Princeton: Princeton University Press 1989.
• H.J. Van der Kaay discusses the threat of emerging pathogens resulting from increased forest loss and contact with primary disease hosts in "Human diseases in relation to the degradation of tropical rainforests," Rainforest Medical Bulletin, Vol. 5, no. 3, Dec. 1998.
• In her work, The Coming Plague (New York: Farrar, Straus, and Giroux, 1994), L. Garrett reviews the gamut newly emerging diseases and suggests the importance of deforestation in bringing some pathogens in closer contact with human populations. For a popular and thrilling account of one such virus, the hemorrhagic Ebola virus, read R. Preston's The Hot Zone (New York: Random House, 1994). S. Morse, ed. also provides a comprehensive overview in Emerging Viruses, New York: Oxford University Press, 1993.
• Y. Baskin discusses the role of human activities in creating new disease vectors in the tropics ("The Work Of Nature," Discover Vol. 16, No. 8, Aug 1995).
• The Rainforest Action Network (RAN 1994) estimates the death rate from malaria among the Yanomani in Brazil and Venezuela at 20%.
• Martin and Lefebvre raise the concern that global climate change will impact the distribution of malaria in "Malaria and climate: sensitivity of malaria potential transmission to climate," Ambio Vol. 24 No. 4, June 1995, while Binder et al. estimates malaria pediatric fatalities in Sub-Saharan Africa in "Emerging infectious diseases: public health issue for the 21st century," Science Vol. 284, No. 5418 (1311-1313) 21-May-1999.
• According to Binder et al., infectious disease is the leading cause of death worldwide and the third leading cause of death in the United States ("Emerging infectious diseases: public health issue for the 21st century," Science Vol. 284, No. 5418 (1311-1313) 21-May-1999).
• The U.S. Centers for Disease Control (CDC) reported to a congressional committee in 1997 that 10% of people who died before the age of 50 in 1994 did so suddenly and mysteriously possibly from some unidentified infection. In addition, the CDC noted that the U.S. spent only $42 million annually on infectious disease surveillance.
• In the World Population Profile: 1998 (U.S. Government Printing Office, Washington, DC, 1999), the U.S. Bureau of the Census revealed the sobering impact of AIDS in the developing world.
• E. Hooper (The River, Boston: Little, Brown and Company 1999) provides an excellent overview of the theories on origin of AIDS. He discusses the merits each of these in the course of describing the OVP/AIDS hypothesis he has come to adopt. This hypothesis says AIDS originated from the contimanation of a live polio vaccine with a simian immunodeficiency virus (SIV) during the mid to late-1950s. The other leading hypothesis, that of a "natural transfer" between SIV-infected chimpanzees and humans, is promoted in a widely read paper by F. Gao et al. ("Origin of HIV-1 in the Chimpanzee Pan troglodytes troglodytes," Nature, Vol. 397 (436-441), 1999).
• At the 7th Conference on Retroviruses and Opportunistic Infections in San Francisco, B. Korber announced that the Los Alamos National Laboratory had traced the divergence of AIDS from SIV to around 1930 (Korber, B. et al., "HIV Databases and Analysis Projects at Los Alamos: An Overview," 1/30/00). The study assumed genetic changes in the virus occur at a constant rate. Should this dating prove correct it would undermine OPV/AIDS hypothesis supported by Hopper 1999.

Citations - Part V

• 1994 figures for exports of primary forest products are included in the State of the World's Forests 1997 (SOFO) published by the United Nations Food and Agriculture Organization (FAO).
• The revenue decline in tropical hardwood exports is estimated in N. Myers "Nature's Greatest Heritage Under Threat." Rainforests-The Illustrated Library of the Earth, N. Myers, ed., Rodale Press: Emmaus, Pennsylvania, 1993.
• The fall in Malaysian and Philippine log exports is documented in the State of the World's Forests 1997 (SOFO) published by the United Nations Food and Agriculture Organization (FAO).
• C.B. MacCerron (Business in the Rainforests: Corporations, Deforestation, and Sustainability, Investor Responsibility Research Center, Washington D.C. 1993) predicts that by 2000 only 10 of the 33 tropical countries that export timber will still be able to do so.
• Myers ("The world's forests: problems and potentials" Environmental Conservation 23 (2) 1996) and D. Pimentel et al. (Pimentel, D., McNair, M., Buck, I., Pimentel, M., and Kamil, J., "The value of forests to world food security," Human Ecology 1996) estimate the value of non-wood forest products at US$90 billion for 1996.

Citations - Part VI

• Norman Myers explains the albedo connection in "The world's forests and their ecosystem services," In Nature's Services: Societal Dependence on Natural Ecosystems ed G.C. Daily, Island Press, Washington D.C. 1997.

Citations - Part VII

• The burning of forests releases almost one billion tons of carbon dioxide into the atmosphere each year according to T.E. Lovejoy in "Biodiversity: What is it?" in Biodiversity II, Reaka-Kudla, Wilson, Wilson, eds.., Washington D.C.: Joseph Henry Press, 1997. The role of deforestation in global warming is further discussed in Peters, R.L. and Lovejoy, T.E., eds. Global Warming and Biological Diversity, New Haven: Yale University Press 1992 and Shukla, J., Nobre, C., Sellers, P., "Amazon Deforestation and Climate Change," Science; 247: 1322-25, 1990.
• In their paper, "Carbon Dioxide Fluxes in Moist and Dry Arctic Tundra during the Snow-free Season: Responses to Increases in Summer Temperature and Winter Snow Accumulation" (Arctic and Alpine Research Vol. 30, No. 4 (373-380), November 1998), Jones, M. H., J. T. Fahnestock, D. A. Walker, M. D. Walker, and J. M. Welker warn that higher temperatures resulting from global warming could result in higher levels of carbon dioxide being released into the atmosphere from arctic tundra.
• E.J. Barron in "Climate Models: How Reliable are their Predictions?" Consequences Vol. 1 No. 3, 1995 describes the phenomenon of the cooling of the stratosphere during warming events.
• Global carbon reserviors are given in Kasting, J.F., "The carbon cycle, climate, and the long-term effects of fossil fuel burning," Consequences Vol. 4, No. 1, 1998.
• W.F. Laurance discusses die-off in forest fragments and the possibly effect on global climate in "Forest Fragmentation May Worsen Global Warming," Science 298: 1117-1118 1/5/98.
• In "Tropical forestry practices for carbon sequestration: a review and case study from southeast Asia," Ambio Vol. 25 No. 4, June 1996, P.M. Costa notes that forest fragments store less carbon per unit of area than contiguous forest because fragments are often comprised of fast-growing tree species which store less carbon per volume than longer-lived trees.
• M. McKloskey ("Note on the Fragmentation of Primary Rainforest," Ambio 22 (4), June: 250-51, 1993) provides the two-thirds figure for global fragmented rainforest.
• In 1995 the Intergovernmental Panel on Climate Change (IPCC) released its report on climate change (Watson, R. T. et al., eds., Climate Change 1995: Impacts, Adaptations, and Mitigation of Climate Change: Scientific-Technical Analyses: Contribution of Panel on Climate Change) concluding "the balance of evidence suggests a discernible human influence of global climate."
• Mann, M.E., Bradley, R.S. and Hughes, M.K. ("Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations." Geophysical Research Letters, Vol. 26 (759-760), 1999) reported the NOAA's findings that 1998 was the warmest year on record. The same paper (picked up by the national press in "Report: 1990s warmest decade of millennium" Reuters 3/3/99) also reported that the 1990s have been the warmest decade of the millennium. J. Warrick in "Scientists See Weather Trend as Powerful Proof of Global Warming," The Washington Post 1/9/98 reported that the past decade has witnessed nine of the eleven hottest years this century.
• The National Research Council of the National Academies (J.M. Wallace et al. Reconciling Observations of Global Temperature Change, National Research Council 2000) examined the apparent conflict between surface temperature and atmospheric temperature, which has led to the controversy over whether global warming is actually occurring and concluded that strong evidence exists to show that surface temperatures in the past two decades have risen at a rate substantially greater than average for the past 100 years. Angell, J.K. further discusses the discrepancies in "Comparison of surface and tropospheric temperature trends estimated from a 63-station radiosonde network, 1958-1998," Geophysical Research Letters, Vol. 26, No. 17 (2761-2764), Sep. 1, 1999.
• L.D. Hatfield provided an excellent overview of the worldwide effects of el Niño in "An Ill Wind Blows in Again," San Francisco Examiner, 9/4/1997.
• The National Oceanic and Atmospheric Administration 1997-2000 reports on the history, frequency, and duration of past el Niño (ENSO) events.
• D.T. Rodbell looks at the history of ancient ENSO events in "An ~15,000-Year Record of El-Nino Driven Alluviation in Southwestern Ecuador," Science, Vol. 283 (516-519), 22-Jan-99.
• Leighton, M. and Wirawan, N found a direct correlation between ENSO events and drought in Eastern Borneo in "Catastrophic Drought and Fire in Borneo Rain Forests Associated with the 1982-83 El Niño Southern Oscillation Event," in G.T. Prance, ed., Tropical Rain Forests and the World Atmosphere., Westview: Boulder, Colorado, 1986.
• The Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) - sponsored by INPE (the Brazilian Institute for Space Research) 1997 - provided data for the global carbon emissions breakdown.
• D. Holt-Biddle in "The Heat is On," Africa-Environment and Wildlife May/June Vol. 2 No. 3. 1994 notes the increase in atmospheric carbon dioxide levels over the past 150 years.
• Martin and Lefebvre discuss the spread to tropical diseases into cooler climes in "Malaria and climate: sensitivity of malaria potential transmission to climate," Ambio Vol. 24 No. 4, June 1995.
• Based a studies of ice cores from Greenland, Steig et al. ("Synchronous Climate Changes in Antarctica and the North Atlantic." Science October 2; 282: 92-95. 1998.) proposed that a chaotic temperature change in Greenland occurred at the end of the last Ice Ages. J. P. Severinghaus and E. J. Brook followed up with similar findings in "Abrupt Climate Change at the End of the Last Glacial Period Inferred from Trapped Air in Polar Ice," Science 1999 October 29; 286: 930-934.
• K.Y. Vinnikov et al. ("Global Warming and Northern Hemisphere Sea Ice Extent," Science 1999 December 3; 286: 1934-1937) found ice in the Artic is shrinking by an average of 14,000 square miles per year and shrinkage is strongly correlated to greenhouse gas and aerosol emissions.
• Mitigating carbon emissions by reforestation is reviewed in E.O. Wilson's The Diversity of Life (Belknap Press, Cambridge, Mass 1992.), Biotic Feedbacks in the Global Climatic System: Will the Warming Feed the Warming? ( New York: Oxford University Press 1995) by G.M. Woodwell and R.A. Mackenzie, eds., and Phillips, O.L. at al. "Changes in the carbon balances of tropical forests: Evidence from long-term plots." Science Vol. 282. October 1998. However this proposition has come under criticism of late by several important agencies including the International Geosphere-Biosphere Programme (IGBP) (B. Scholes, "Will the terrestrial carbon sink saturate soon?" Global Change NewsLetter No. 37:2-3, March 1999) and the Intergovernmental Pannel on Climate Change (R. Watson et al. IPCC Special Report on Land Use, Land Use Changes, and Forestry, 1999).
• Parry, M. et al. ("Adapting to the Inevitable," Nature Vol. 395 22-Oct-1998 "(741)) conclude the cuts under the Kyoto Protocol would only shave off 0.1°F by 2050.
• In "Bogging Down in the Sinks" (Worldwatch Nov/Dec 1998) A.T. Mattoon discusses some of the problems with forestry sinks under the Kyoto protocol.
• Agricultural changes brought on by climate change are considered by R.C. Rockwell in "From a carbon economy to a mixed economy: a global opportunity," Consequences Vol. 4 No. 1, 1998 and at the Global Change and Terrestrial Ecosystems Focus 3 Confrence (1999). Several studies presented at this confrence suggest that grain grown under carbon dioxide enriched conditions maybe less nutritious than than grain grown under current conditions. This conference was arranged under the International Geosphere-Biosphere Programme (IGBP).
• R. Monastersky in "Acclimating to a Warmer World," (Science News, Vol. 156. 28-Aug-99) reviews some of the pitfalls and windfalls from a warmer climate including an increase in number of "hot" days, sewage and transit problems, and lower heating bills.
• A.E. Waibel et al. ("Arctic Ozone Loss Due to Denitrification," Science Vol. 283 No. 5410 (2064-2069), March 26, 1999) showed that global warming could slow the recovery of the ozone layer.
• Houghton (Houghton, R.A. "Tropical deforestation and atmospheric carbon dioxide," in: Tropical Forests and Climate, ed. N. Myers., Dordrecht: Kluwer Academic Publishers, 1992 and Houghton, R.A., "Role of forests in global warming," in: World Forests for the Future: Their Use and Conservation, ed K. Ramakrishna and G.M. Woodwell, New Haven: Yale Univseristy Press, 1993) and Myers (Myers, N., "The world's forests: problems and potentials," Environmental Conservation. 23 (2), 1996) estimate carbon sequestration by the reforestation of 3.9 million square miles (10 million square km).

Citations - Part VIII

• Some good overviews of the current concerns over species extinction can be found in Pimm, S.L., Jones, H.L., and Diamond, J. "On the risk of evolution," American Naturalist, 132 (6) 757-785, 1988; Simberloff, D.S., "Are We on the Verge of a Mass Extinction in Tropical Rainforests?" in D.K. Elliot, ed. Dynamics of Extinction, New York: Wiley 1986; Wilson, E.O. "The current state of biological diversity." In BioDiversity, Wilson, E.O. and Peter, F.M., eds. National Academy Press, Washington D.C. 1988; Wilson, E.O. "Threats to Biodiversity," Scientific American, Sept, 1989; Wilson, E.O. "Wildlife-Legions of the Doomed," Time Magazine, 1991; Wilson, E.O., The Diversity of Life, Belknap Press, Cambridge, Mass. 1992.
• May, E. M., Lawton, J.H., Stork, N.E. compare the estimated current extinction rate to the background extinction rate in "Assessing Extinction Rates" in Extinction Rates, Lawton and May, Eds., Oxford: Oxford University Press, 1995 in Biodiversity II.
• T.C. Whitmore ("Tropical Forest Disturbance, Disappearance, and Species Loss," Tropical Forest Remnants: Ecology, Management, and Conservation of Fragmented Communities, W.F. Laurance and R.O. Bierregaard, Jr, Eds., Chicago: University of Chicago Press, 1997) notes that while there is little evidence of the mass extinctions predicted by the species-area curve, extinction probably has a time lag so species loss from habitat destruction in the past is not yet apparent.
• In his book The Call of Distant Mammoths: Why the Ice Age Mammals Disappeared (Copernicus New York. 1997), P.D. Ward provides a popular account of the extinction of Ice Age megafauna. He explores the leading extinction theories and reviews terminology associated extinction such as "extinction debt." For more detailed examination of extinction debt, see McCarthy, M.A., Lindenmayer, D.B., and Drechsler, M. "Extinction debts and risks faced by abundant species." Conservation Biology Vol. 11 No. 1 (221-226), Feb. 1997 and Tilman, D. et al. "Habitat destruction and the extinction debt." Nature 371: 65-66. 1994. Recently Cowlishaw, G. ("Predicting the Pattern of Decline of African Primate Diversity: an Extinction Debt from Historical Deforestation." Conservation Biology, Pages 1183-1193. Vol. 13, No. 5, October 1999) examined extinction debts among west African primates, while Brooks, T.M., Pimm, S.L., and Oyugi, J.O. ("Time Lag between Deforestation and Bird Extinction in Tropical Forest Fragments." Conservation Biology, Pages 1140-1150. Vol. 13, No. 5, October 1999) surveyed the extinction debt-time lag among insular Southeast Asian bird species.
• Comparing the occurrence of bird species in isolated forest fragments with the original avifauna Renjifo, L.M. ("Composition Changes in a Subandean Avifauna after Long-Term Forest Fragmentation." Conservation Biology, Pages 1124-1139. Vol. 13, No. 5, October 1999) found a reduction in diversity after fragmentation.
• The species extinction table is derived from a similar table in Biodiversity II, Reaka-Kudla, Wilson, Wilson, eds.., Washington D.C.: Joseph Henry Press, 1997. The extinction estimates come from several sources including Raven, P.H. "Our Diminishing Tropical Forests," In BioDiversity, Wilson, E.O. and Peter, F.M., eds. Washington D.C.: National Academy Press, 1988; Wilson, E.O. "Threats to Biodiversity," Scientific American, Sept, 1989; May, R.M., "How Many Species Are There on Earth?" Science, 241: 1441-49, 1988; Wilson, E.O. The Diversity of Life, Cambridge, Mass.: Belknap Press, 1992; Reid, W.V. "How Many Species Will There Be?" In Tropical Deforestation and Species Extinction, Whitmore, T.C. and Sayer, J.A., eds., London: Chapman and Hall, 1992; and Mace, G.M.; 1994; "Classifying threatened species: means and ends," Phil. Trans. R. Soc. Lond. Bulletin 344, 91-97; Lovejoy, T. E. "A projection of species extinctions," in The Global 2000 Report to the President, G.O. Barney, Study Director, Entering the twenty-first century, vol. 2. Council on Environmental Quality,U.S. Government Printing Office, Washington D.C. 1980; From Biodiversity II. Reaka-Kudla, Wilson, Wilson, eds. Joseph Henry Press. Washington D.C. 1997; and Lovejoy, Thomas E. "Biodiversity: What is it?" In Biodiversity II, Reaka-Kudla, Wilson, Wilson, eds.., Washington D.C.: Joseph Henry Press, 1997.
• The worldwide decline in amphibians is discussed by Lips ("Decline of a montane amphibian fauna," Conservation Biology Vol. 12 No. 1 (106-117), Feb. 1998.), Sessions et. al. (Sessions, S.K. Franssen, R.A., Horner, V.L., "Morphological Clues from Multilegged Frogs: Are Retinoids to Blame?" Science. 284 (5415) 1999), Tangley ("The Silence of the Frogs," U.S. World and News Report 8/3/98.), and Tuxill ("The Latest News on the Missing Frogs," World Watch, May/June 1998.).
• Population sinks and sources are discussed in Merenlender, A., Kremen, C., Rakotondratsima, M., and Weiss, A., "Monitoring Impacts of Natural Resource Extraction on Lemurs of the Masoala Peninsula, Madagascar," Conservation Ecology Vol. 2(2): No. 5, 1998.
• Suplee, C. reported the findings of the IUCN that roughly 12% of the world's flora can be classified as being threatened with extinction ("One in Eight Plants in Global Study Threatened," The Washington Post, 4/8/98).
• In their The Theory of Island Biogeography (Princeton, New Jersey: Princeton University Press, 1967) R.H. MacArthur and E.O. Wilson discuss the geographic distribution and number of species of species on islands of varying sizes and vegetation types.
• Mass extinctions are defined in Sepkoski, J.J. "Mass extinctions in the Phanaerozoic oceans: A review," Geological Society America, Special Paper 190, 1982, and Ward, P.D., On Methuselah's Trail: Living Fossils and the Great Extinctions, New York: W.H. Freeman and Company, 1992 and further explored in Raup, D., The Nemesis Affair, New York: W.W. Norton, 1986 and Martin, P.S. and Klein, R.G., eds., Quaternary Extinctions: A Prehistoric Revolution, Tucson: University of Arizonia. 1984.
• The role of extra-terrestrial objects in past extinction events is evaluated by Alvarez et al. (Alvarez, L., Alvarez, W., Asaro, F., and Michel, H., "Extra-terrestrial cause for the Cretaceous-Tertiary extinction," Science 208: 1094-1108, 1980), Gore (Gore, R., 1989, "Extinctions," National Geographic, Vol. 175:6, p. 662-698), Raup (Raup, D., Extinction: Bad Genes or Bad Luck? New York: W.W. Norton; 1991), Sheehan (Sheehan, P.M., 1991, "Sudden extinction of the dinosaurs: latest Cretaceous, Upper Great Plains, U.S.A.," Science, v. 236, p. 835-839), and Hecht (Hecht, J., 1993, "Asteroidal bombardment wiped out the dinosaurs" New Scientist, v. 138, p. 14).
• Forces (demographic stochasticity, environmental stochasticity, and reduced genetic diversity) that can drive a species with a population under MVP to extinction are explored in The Call of Distant Mammoths: Why the Ice Age Mammals Disappeared (New York: Copernicus, 1997) by P.D. Ward and in Conservation and Biodiversity, New York: Scientific American Library, 1996 by A. Dobson.
• The concept of minimum viable populations is developed in Soulè, M.E. and Wilcox, B.A., eds., Conservation Biology: An Evolutionary-Ecological Perspective, Sunderland: Sinauer 1980; in Frankel, O. and Soulè, M.E. Conservation and Evolution, Cambridge: Cambridge University Press, 1981; and in Gilpin, M E. and Soule, M.E. (1986). "Minimum viable populations: the processes of species extinction," In Conservation Biology (pp. 19-34), Sunderland, MA.: Sinauer Associates, M. E. Soule (Ed.). Gilpin has continued to apply mathematical physics and operations research in his approach to examining island biogeography and population genetics in several books (including Restoration Ecology. (1987). J. Aber, M. Gilpin and W. Jordan, Eds. Cambridge University Press, London; Metapopulation Dynamics: Theoretical Models and Empirical Investigations. (1991). M. Gilpin and I. Hanski, Eds. Academic Press, New York; and Metapopulation Dynamics: Genetics, Evolution and Ecology. (1996). I. Hanski and M. Gilpin, Eds. Academic Press, New York).
• The role of social dysfunction in population extinction is considered in Raup, D., Extinction: Bad Genes or Bad Luck? New York: W.W. Norton, 1991, and R.B. Primack, Essentials of Conservation Biology, Sunderland, MA.: Sinauer Associates, 1993.
• Alfred Wallace's concerns over biodiversity loss in Indonesia during the late 19th century can be found in his classic Island Life (1881) (reprint edition (December 1997) Prometheus Books).
• The complexity of ecosystem dynamics and population fluctuations is discussed in M. Gilpin and I. Hanski, Eds., Metapopulation Dynamics: Theoretical Models and Empirical Investigations (1991). Academic Press, New York; May, R. and Nowak, M. "Superinfection, metapopulation dynamics, and the volution of diversity" Journal of Theoretical Biology 170: 95-114, 1994; Leakey, R. and Lewin, R., The Sixth Extinction: Patterns of Life and the Future of Humankind. New York: Doubleday, 1995; I. Hanski and M. Gilpin, Eds. Metapopulation Dynamics: Genetics, Evolution and Ecology. (1996). Academic Press, New York; and Ward, P.D. The Call of Distant Mammoths: Why the Ice Age Mammals Disappeared (New York: Copernicus 1997).
• Holdgate (Holdgate, M., "The Ecological Significance of Biological Diversity," Ambio Vol. 25 No. 6, Sept. 1996) notes that only 724 species have been recorded as going extinct since 1600, but explains actual extinction rates are acutally considerably higher given our relative ignorance of the number of species and inter-relationships between species.
• Wilson (Wilson, E.O., The Diversity of Life, Cambridge, Mass.: Belknap Press 1992) and Erwin (Erwin, T. L. "Tropical Forests: Their Richness in Coleoptera and other arthropod species." Coleopterists Bulletin 36:74-75. 1982) estimate that roughly half the world's species dwell in rainforests.
• Critics (see "Truth Almost Extinct in Tales of Imperiled Species," The Washington Times, September 19, 1984, and Simon, Julian, and Aaron Wildavsky (1994). Species Loss Revisited. Endangered Species Blueprint (National Wilderness Institute) 5, 1: 6-9.) have argued that the "extinction crisis [based on these theoretical projections] is alarmist and exaggerated" (Brooks, T., Pimm, S.L., Collar, N.J., "Deforestation predicts the number of threatened birds in insular southeast Asia," Conservation Biology Vol. 11 No. 2, April 1997).
• Ward, P.D. (The Call of Distant Mammoths: Why the Ice Age Mammals Disappeared (New York: Copernicus 1997) provides commentary on the Moisimann and Martin model of 1975 and its later amendment by Whittington and Dyke in 1989.
• In his article "The Big Goodbye" (Outside, November 1981) D. Quammen articulates that the intricate relationships between species may result in the extinction of a large number of species.
• E.O. Wilson laments the loss of biological diversity in The Diversity of Life. (Cambridge, Mass.: Belknap Press, 1992) noting that as each species is lost, a unique combination of genes - which has been produced over the course of millions of year - also disappears.
• Norman Myers popularized the subject of the current extinction wave in The Sinking Ark. A New Look at the Problem of Disappearing Species, New York: Pergamon, 1979.
• In his book The Future Eaters (New York: Braziller 1995.) T.F. Flannery provides a fine overview of ancient man's impact on the ecology and environment of Australia. He holds mankind largely responsible for the extinction of Australia's megafauna.
  
  Easter Island
  
  
• In his article "Easter's End" (Discover. Vol. 16, No. 8, Aug 1995) Jared Diamond evinces that the social collpase of Easter Island may be tied to its ecological degradation and subsequent impoverishment. This interesting and very readable article provides the substance for the text box on "Historical Consequences of Deforestation: Easter Island."
• Steadman, D. W. ("Extinction of Birds un Eastern Polynesia: A review of the record, and comparisons with other Pacific Island groups," Journal of Archaeological Sciences, 16:177-205, 1989. From Biodiversity II, Reaka-Kudla, Wilson, Wilson, eds., Washington D.C.: Joseph Henry Press 1997). notes that only one of the original 22 species of seabird still nests on Easter Island.
• For a larger scale perspective than Easter Island, C. Runnels, "Environmental degradation in ancient Greece," Scientific American 272 (3): 72-75, 1995 and R. Adams, Heartland of Cities, Chicago: University of Chicago Press, 1981 link environmental degradation with the decline of civilization in ancient Greece and Mesopotania, respectively.