Keystone Species Extinction Overview

Keystone Species Extinction Overview

Paul Alois and Victoria Cheng, July 2007


Human beings have recklessly exploited the resources on this planet and continue to do so despite the obvious widespread negative consequences. Due to the severe effects of human expansion in the last 10,000 years, some scientists now believe that the Earth has entered a new “extinction phase”.[1] According to the World Resources Institute, the current rate of species extinction is between 50 and 1000 times more than the geo-historical norm.[2] The World Conservation Union’s (IUCN) Red List reports that of the 40,117 species the organization examined, 16,119 were in danger of extinction: one in eight species of birds, one in three of amphibians, and one in four of mammals.[3]

Considering the convenience of modern life, it is easy for people to forget that they rely on natural ecosystems to live as much as other animals do. Advances in the production and distribution of food in the last fifty years have created the impression that humans have mastered their environment, but that is far from being the case. In recent years it has become apparent that much of the progress made in the past several decades came with a price. The ecosystems that human beings depend on for their very survival have been radically undermined, and today many of them appear to be on the verge of breaking down.

The most recent paradigm in ecological sciences posits that environmental change happens in a rapid, non-linear fashion. This paper will examine certain species of organisms that have the potential, once their numbers are low enough, to trigger a sudden collapse in the cycles that provide human beings with food.

1. Aquatic Systems

1.1. Plankton

Plankton is a blanket term for many species of microorganisms that drift in open water and make up the base of the aquatic food chain. There are two types of plankton, phytoplankton and zooplankton. Phytoplankton make their own food through the process of photosynthesis, while zooplankton feed on phytoplankton. Zooplankton are in turn eaten by larger animals. In this way these tiny organisms sustain all life in the oceans. According to the NASA, phytoplankton populations in the northern oceans have declined by as much as 30% since 1980.[4] While the cause of this decline remains uncertain, there are several theories.

One theory points to global warming as the main cause.[5] Phytoplankton require nutrients obtained from the bottom of the ocean to reproduce. At the Earth’s poles, ocean water is colder at the surface than down in the depths. Therefore water from the bottom of the ocean rises to the top, carrying with it essential nutrients from the ocean floor. However, as the water near the surface becomes warmer due to climate change, less water rises from the bottom, resulting in less nutrients for the phytoplankton. This consequently hinders their reproduction processes.

Another theory suggests that carbon dioxide emissions are causing this decline in plankton population. The ocean has always absorbed a significant amount of carbon dioxide, but in recent years its capacity for this pollutant may not have been able to keep up with the level of human output. Recent studies suggest that the carbon dioxide the ocean absorbs is turned into carbonic acid, which lowers the pH level of the ocean.[6] This acidification is highly corrosive to sea animals that form shells, including pteropods, which are a type of zooplankton. Pteropods are a food source for countless larger animals such as salmon and cod. If they are unable to survive in an acidic ocean, then the entire ocean system will be threatened.

A less popular theory suggests that a lack of iron is damaging plankton populations. All the nutrients necessary for phytoplankton reproduction exist all throughout the ocean, except for iron, which is can only be found in certain locations. Therefore, phytoplankton are limited to areas where iron is found. Studies have shown that a major source of iron comes from the dust that is swept off the world’s deserts into the ocean.[7] Increased human activities may be altering the cycle in which desert iron reaches the ocean, therefore cutting phytoplankton off from nutrients vital to their survival.[8]

The declining plankton population is a very serious issue. In 1997, El Niño caused a sharp increase in the ocean’s temperatures around the Galapagos Islands.[9] Plankton populations plummeted, and this in turn decimated fish populations. The island’s famous seal population, which depended on the fish for food, also decreased. As El Niño passed, the ecosystem rebounded, but the event was a clear indicator of the severe effects that a plankton extinction would have. Researchers in California fear that a similar disaster may be occurring throughout the entire northern Pacific Ocean. If the decimation of plankton population is caused by global warming, and researchers warn that its impact could be permanent.[10]

1.2. Edible Fish

Meanwhile, over the last fifty years the top of the food chain has been destabilized by the modern commercial fishing industry. According to the World Watch Institute, the world’s wild fish harvest increased from 20 million tons in 1950 to 87 million tons in 1997.[11] At that point, the upward trend reversed because fish population growth could not keep up with the losses, and by 2003 only 77.7 million tons of fish were caught in the wild.[12]

One of the clearest indicators of the present crisis can be found in Japan. Japanese fishing boats traverse every one of the world’s oceans, and the fishermen have been keeping meticulous records for decades. They use a technique called longline fishing, which consists of dragging fishing lines with hundreds of hooks behind the boats. When longline fishing began after WWII, fishermen caught 10 fish per 100 hooks; now, because of the decline in the fish populations, they are lucky to catch even one.[13]

Recently, scientists predicted the total collapse of all edible fish species in the ocean by 2050.[14] Their study blames commercial fishing, pollution, and loss of diversity of fish species as the main causes of this destruction. Among freshwater fish there is no analogous projection, but the IUCN has put freshwater fish at the top of its list of endangered species.[15] Studies examining whether or not species can rebound from low populations have had mixed results. The scientists cited above believe that many oceanic species could recover in ten years or less, provided that they are not fished to extinction.[16] However, in the frequently cited case of Newfoundland cod, a ban on fishing has done little to help the population’s extremely low numbers.

Overfishing is not the only problem, however: fish populations are also being affected by global climate change, which is causing the temperatures of lakes, rivers, and oceans to rise. Since oxygen is more plentiful in colder water, warmer waters would mean less oxygen for fish populations. Certain fish such as salmon cannot reproduce if the water temperature deviates too much from a certain range.[17] A recent study conducted by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) have concluded that the temperature of the coastal waters of Australia will rise by two degrees by 2030.[18] This would make certain marine organisms such as fish, jellyfish, and turtles move towards colder waters south of Australia. Fishing industries, consumers, and animals who depend on the fish for food, such as birds and sea predators, would suffer as well..[19] This phenomenon is taking place in waters all over the world.

Ecosystems are highly dynamic: a slight change in the population of any species sets off a ripple effect throughout the whole system, making it very unlikely that the damage can simply be undone. If the threats of overfishing and climate change to the fish population are not removed, instabilities in the system could have serious and devastating impacts on human beings as well as other animal species.

2. Terrestrial Systems

2.1. Bees

Bees are central to the systems that support food production for human beings. An international study of 115 food crops grown in over 200 countries showed that 75% of the crops were pollinated by animals, especially by bees.[20] According to the International Bee Research Association, bees pollinate 80% of the food grown in the United Kingdom.[21] Bees play such an integral role in maintaining many of the planet’s ecosystems that Albert Einstein once said, “If the honeybee goes extinct, we have four more years on Earth.” Both domesticated bees and wild bees contribute significantly to global pollination, but unfortunately both are facing threats to their survival.

Domesticated bees serve a vital economic function. Farmers can no longer just depend on wild bees to adequately pollinate their crops, so they must rent domesticated bees for that purpose in the spring. Without a sufficient supply of domesticated bees, crops simply would not be able to reproduce. The total economic value of domestic bees in the world is unknown, but in North America alone they support tens of billions of dollars of agricultural products.[22]

The domestic bee population worldwide is being threatened by several factors. In 1987 apiarists in the United States began noticing that domestic hives were being infested with small mites. Without interference, the mites could destroy a colony of bees in as little as two weeks. The mites are dangerous to bees in two ways. First, they hide in the cells of bee larvae and inhibit the larvae’s development. A colony infested with mites often has many juvenile bees with missing legs or wings or with deformed body segments. Secondly, the mites can bore holes in the exoskeletons of adult bees, making them extremely susceptible to viruses. Scientists believe that these mites originated in Asia, where the native bee population has developed a resistance to them.[23] But American bee populations have not been so lucky, and they continue to face this threat to their existence.

In the last several years apiarists and scientists have been documenting a very strange phenomenon they label “colony collapse disorder” (CCD). A hive affected by CCD may appear normal at first glance, but upon closer inspection almost all of the adult bees in the hive have vanished. These hives usually contain a large amount of stored food, and many cells are filled with larvae that are being cared for by juvenile bees.

There are two aspects of CCD that leave apiarists extremely puzzled. First, there are no bodies of dead adult bees in or around an affected hive, which is to be expected if the hive has been infected with a disease. Secondly, other bees do not take over the affected hive for two weeks or more. This is especially strange as ordinarily a strong bee colony will colonize a weaker neighbor immediately. Scientists studying CCD are unable to pinpoint a cause, but they have noticed that all the affected hives were subjected to constant migration. They suggest that the process of transporting the hive may weaken the colony in some way.[24] The number of hives affected by CCD exploded exponentially in the US in 2006, and if this trend continues it will seriously jeopardize human food production.

Wild bee populations are also being directly threatened by human activity, which has caused bee habitat loss and their exposure to poisonous pesticides. Many bee habitats have been destroyed to make room for crops. Ironically, the crops which are then planted depend on bee pollination to reproduce: without wild bees to do the job, farmers are then forced to rent domestic bees. Furthermore, the heavy use of pesticides also damages wild bee colonies, which again hurts crops and farmers.

Bees need pollen from specific types of flowering plants, and sometimes these plants only flower during certain times of the year. If a bee population’s habitat is changed or destroyed by human activity, and other types of plant life are introduced to the environment, the bee population may not be able to survive. Also, bees make their homes in particular environments, whether it in decaying logs or burrows in the ground or hives in trees. If the bees cannot find a suitable site for their home because of habitat loss due to anything from natural disaster to human activity, then they are also threatened.[25]

Pesticides are sprayed onto crops to protect them from diseases, foraging insects, and other animals. Sometimes bees are sprayed directly with pesticides and die at a distance from the hive. But if a bee takes pollen or nectar from chemically-treated crops back to the hive, many bees would be affected.[26] Also, pollen is kept in honeycombs to feed the young bees, so contaminated pollen would kill the youngest generation as well, threatening the future of the bee colony. Since bees often forage for food miles away from the hive, it is susceptible to pesticides sprayed on crops within a wide radius.

Therefore, bees face threats from both natural parasites, strange diseases, and human activity. If something is not done to protect both domestic and wild bee populations, agriculture and even natural plant growth could be compromised.

2.2. Topsoil

While topsoil is not a living organism, it is the foundation of the Earth’s terrestrial ecosystems and is loosely analogous to plankton. Topsoil refers to far more than just dirt: it is actually a very complex micro ecosystem made up of numerous different forms of life. One teaspoon of topsoil contains 5 billion bacteria and 20 million fungi; a square meter can contain 12 million nematodes, 120,000 mites, 20,000 pot worms, 8,000 slugs and snails, 2,000 earthworms, and thousands of insects of various species.[27] It can take centuries for just an inch of topsoil to form naturally, and careless destruction of the existing topsoil cannot be easily reversed.

Without healthy topsoil, food production is virtually impossible. Ironically, the main cause of soil degradation has historically been agriculture. Consumption of food has increased globally, yet this increase is only destroying topsoil at a faster rate. The United Nations Environment Program estimates that over the last 10,000 years, 2 billion hectares of productive land have been destroyed by human activities.[28] When compared to the 1.5 billion hectares of land being used for agriculture today, that number is very significant. Soil degradation has the potential to threaten global food security, and it is already a major issue in many parts of the world today.

According to the United Nations, of the 1.5 billion hectares of land being used for agriculture, 38% of that land is experiencing moderate to severe topsoil degradation.[29] The most affected areas are in Africa and Central America, while the least affected areas are in Europe and North America. The biggest cause of soil degradation is erosion, although nutrient depletion, salination, and pollution also play a role. The effect that soil degradation has had on food production is difficult to quantify from a global perspective, but there is no doubt that this is a serious issue, particularly in the developing world.

In India, 38% of agricultural land is severely affected by water erosion.[30] Despite having one of the highest population densities on the planet, India’s total population is still increasing rapidly. Furthermore, the country has a large rural population that is dependent on farming. Soil erosion coupled with water shortages has the potential to seriously cripple India’s ability to feed its rising population.

A prominent Chinese minister recently said that soil erosion is China’s number one environmental problem.[31] Over 38% of China’s territory is affected by either wind or water erosion.[32] 7% of the world’s cultivable land is in China, yet this land must support 24% of the world’s people.[33] Water erosion is most serious in China’s “rice bowl,” located between the basins of the Yangtze and Yellow Rivers. Every year over 4.5 billion tons of soil is swept into the two rivers, damaging agricultural output and raising the level of the river beds. Wind erosion, also known as desertification, has already converted 17.6% of China’s landmass into useless desert.[34] The cost to China’s economy from soil erosion is easily in the tens of billions of dollars.

Sub-Saharan Africa has the world’s highest rate of soil degradation. This problem is compounded by the region’s extremely high poverty rates and the large number of subsistence farmers. In the coming decades the number of people without adequate access to food in sub-Saharan Africa is expected to grow substantially.[35] While soil degradation is not the only factor causing this food shortage, it is a significant one.

The loss of precious topsoil is a problem affecting many regions of the globe, and it has the potential to seriously threaten food supplies worldwide. Like many other resources, topsoil is limited and difficult to replace, and it is imperative to preserve the topsoil that is still in existence.

3. Conclusion

The preservation of the fundamental cornerstones of the ecosystem must become a foremost goal in human advancement, and it is clear that their destruction must be stopped. Plankton supporting abundant sea life are dying, fish that is a staple part of the diet of many people around the world are being fished to extinction, bees pollinating crops are threatened by many factors, and topsoil sustaining agriculture is disappearing. To solve these problems, people must also address bigger problems caused by human activity such as climate change, the destruction of habitats, and the depletion of resources due to careless use. If any of these species examined should be reduced to a low enough level, consequences for our own survival would be profound. The loss of these actors is happening rapidly, and it is crucial that this be stopped and reversed as soon as possible.

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[2] Millennium Ecosystem Assessment, 2005 Ecosystems and Human Well-being: Synthesis pg.5

[12] World Watch Institute, Vital Signs, 2006-2007, pg 26

[15] Ibid: footnote 3

[16] Ibid. 14

[20] “Importance of Pollinators in Changing Landscapes for World Crops”, Klein, Vaissiere, Cane, et al, submitted to the Royal Society of London

[27] “The Ecology of Eden”, by Evan Eisenberg, copyright 1998, published by Alfred A. Knopf pg 23

[28] “Soil Degradation” by Sara J. Scherr, IFPRI, discussion paper 27, pg 17

[29] Ibid 23, pg 18

[33] Laszlo, Ervin. The Chaos Point: The World at the Crossroads.


[35] “Linking Land Quality, Agricultural Productivity, and Food Security” by Keith Wiebe, published by US Dept. of Agriculture, Agricultural Economic Report, No. 823