An example of what was happening before regulation can be seen in the case of crocodilian skins, used for making specialty leathers. During the 1950's and 1960's, 5-10 million skins were traded internationally each year. The intense hunting pressure drastically reduced the numbers of the most desirable species, the American Alligator and Orinoco Crocodiles of Latin America. As these species became scarce, hunters turned their attention to the black caiman and the broad-snouted caiman, then to the spectacled caiman. By the late 1960's, all of these species except the spectacled caiman were considered endangered. Trading was down to ~500,000 per year in the 1990s, one tenth of the previous level.

Many fur-bearing animals, including the cheetah, many other species of cats, chinchilla, vicuna, giant otter, and some monkeys, have declined to very low levels because of hunting for their furs, which were traded on the international market.

Several valuable tree species, including West Indian mahogany, Caoba mahogany of Ecuador, and Lebanese cedar, have been reduced to a few scattered ruins of forest.  Collectors have seriously depleted many orchids in the wild, and many tropical fish and birds have been threatened by overhunting for the pet trade.

SMUGGLING AND WILDLIFE CRIME WEBSITE

CITES

International trade puts enormous economic pressure on suppliers and threatens the existence of many rare plants and animals. For this reason in 1975 the U.S., along with nine other countries, signed the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The objective of CITES, which now involves over 150 countries, is to ensure that trade will not cause the extinction of plant or animal species.

The Convention has three important appendices that are periodically revised:

Appendix I contains the species that are threatened with extinction. All commercial trade is banned for these species, but noncommercial trade is allowed if it does not jeopardize the species' survival in the wild. Permits are required for the exportation and importation of Appendix I species.  Examples:

 

Great apes  Great whales  African elephant  All rhinoceros species  All tiger subspecies Large cats Giant Panda

Many parrots All sea turtles Most crocodilians Several orchids, cacti and cycads

Total 510 animal plus 320 plant species (1997)

Appendix II contains a longer list of species which are not now threatened with extinction, but for which uncontrolled commercial trade would be detrimental.  Trade in these species is strictly regulated through the use of export permits. Examples:

All of the following not on Appendix I: Primates (apes, monkeys, lemurs) Cats Parrots Crocodilians Cacti Orchids

Plus: Black bear Various snakes and lizards Poison-arrow frogs Some butterflies Some corals

Total 4061 animal plus 25161 plant species (1997)

Appendix III includes species where there is some question as to the potential negative impact of commercial trade. Permits are used to monitor trade in these species.

Any listing of a species in either Appendix I or II requires approval by two-thirds of the CITES party countries, but any Convention member may place a native species on Appendix III.

Animals threatened by International Trade 

Tigers

It has been estimated that all of the world's tiger and rhino species will be extinct within just a few years if trade in their parts is not eliminated. The main markets for tiger parts are China, Taiwan and South Korea. Tiger bones are used to make a broth for treating rheumatism, muscle cramps and rabies, while tiger penis soup, selling for up to $320 a bowl, is sold as an aphrodisiac. Tiger bristles, the musk gland and skins are all highly valued. Sometimes the poachers have taken only bones and genitals, leaving the skins to rot. This is probably because it is much more difficult for enforcement agencies to identify the bones than the skins.  

Three of the eight species of tiger are already extinct and all the others are threatened because of a combination of habitat loss and poaching for the Asian traditional medicine market. The total tiger population has declined by 95% in the 20th century, leaving only about 5,000. See table for individual species. The Siberian tiger, with only 200 animals, could be extinct within a few years if China does not take effective measures immediately. China recently created a National Tiger Reserve to protect one population of less than six of the animals. The Indian tiger (Bengal tiger) down to about 3,000 animals which is less than 10% of pre-exploitation population, could be extinct within ten years because of illegal hunting in India to supply the demand for tiger bones in China.

 

Species	Population
Bali tiger	Extinct, 1940s
Caspian tiger	Extinct, 1970s
Javan tiger	Extinct, 1980s
Sumatran tiger	400
South China tiger	20
Siberian tiger	200
Indo-Chinese tiger	1,000
Bengal tiger	3,000

 

See Audubon magazine, March-April 1997 for a good review by Peter Matthiessen on the Last Wild Tigers. World Wildlife Fund declared 1998 the Year of the Tiger. 23 countries including Bangladesh, China, India, Indonesia, Malaysia, Nepal, Russia, Thailand and Vietnam supported a resolution at the 1994 CITES conference, calling for urgent action in 15 critical areas of tiger conservation. But a study carried out in 1997 showed that the governments of these countries had largely ignored the recommendations. For example, only two countries had enacted laws prohibiting domestic trade in tiger derivatives since the resolution, and only seven had done so earlier.  Thailand has a thriving trade in tiger parts because of failure to enforce laws prohibiting it.

Tigers In Trouble

Giant Pandas

Another animal that might be driven to extinction by illegal hunting is the giant panda, down to about 1,000 animals in Sichuan province, China. One skin (usually used just as a wall hanging) is worth $40,000 on the black market in Japan, Hong Kong and Taiwan. These animals are also in demand from zoos - In 1995 San Diego Zoo got permission to import a pair of pandas from China, in return for paying $1 million a year to support panda habitat protection in China (when the zoo had pandas on loan for six months in 1987 and 1988, their revenue increased by $4 million!). The pandas only have one mating season per year, and the San Diego pair did not mate.  One cub was born in August 1999 following artificial insemination.  Twenty other zoos in this country are now planning to bring in pandas. The Department of the Interior will require them to spend any additional income generated by their panda exhibits on endangered species conservation. The giant panda is listed as an endangered species under the U.S. Endangered Species Act, meaning that it considered in danger of extinction throughout all or a significant portion of its range. This also makes it illegal to import giant pandas into the U.S. except under certain conditions.   It is also protected under CITES.

Rhinos

90% of the world's population of the five species of rhinoceros has disappeared since 1970 as a result of poaching for rhino horn (actually not a real horn but a growth from the skin of densely compressed keratin fibers - the same material as in hair and nails).  Rhino horns sell in China, Taiwan, South Korea and the Middle East for prices over $44,000 each - it really is worth more than its weight in gold!

In Eastern Asian countries, powdered rhinoceros horn is used as a remedy for many ills, including nosebleeds, headaches, diphtheria and food poisoning. But it is also very popular because it is thought to have aphrodisiac properties.  This use is thought to have originated from the idea, going back to Roman times, that consumption of animal genitalia is an effective way to treat sexual problems ("organotherapy").  Even today in China there is a market for animal genitalia. One Canadian company delivered 50,000 seal carcasses to China during 1994. The genitals of a seal were worth more than $100, while the skin, meat and oil were worth only $20.

Obviously rhino horn has nothing to do with genitalia.  Apparently the origin of the confusion is that dried rhino penis was used as an aphrodisiac in organotherapy, and buyers confused the horn with the other organ.

The use of rhino horns (and tiger bones) for medical purposes was declared illegal in China in 1993. But illegal trade continues because of the extremely high value of these items.

Black rhino.  The population of the Black rhinoceros of East Africa dropped precipitously from 65,000 in 1972 to 1,900 in 1993. The most endangered rhino subspecies, the Western black rhino (Diceros bicornis longipes) is down to less than 15 animals in Cameroon, where each animal has been assigned a private armed guard to protect it from poachers.

White rhino.  7,500 animals remain of the southern subspecies of White Rhinoceros, mostly in South Africa. Only about 25 individuals of the northern subspecies of the White rhinoceros remain alive in the world, and these last survivors are threatened by violence and armed conflict in the Democratic Republic of Congo.  

Indian rhinos (the "Great One-horned Rhinoceros") are down to about 1,900, Asian rhinos are even more threatened. Only a few hundred Sumatran rhinos and 70 Javan rhinos remain.

When the government of Zimbabwe realized that both black and white rhino populations had been reduced to dangerously low levels, in 1992 they began amputating the horns in order to increase the rhino's chances of survival. A year later, 140 black rhinos out of 305 remaining in the country, and 123 white rhinos out of 198 remaining, had been dehorned. Unfortunately, this did not stop poachers from killing rhino - in 20 months 10 dehorned whites and six dehorned blacks were killed by poachers. Not all of the horn can be removed, and the horn is so valuable that it is worth killing the rhino just for the stump. Also, the horn regenerates at about 3" per year. And after stalking a rhino, the hunters will often kill it even if it has no horn, so they will not waste any more time in hunting and following the same animal again. At the same time that poaching has been increasing Zimbabwe has had to lay off 250 scouts and to scale back anti-poaching patrols in order to save money.

Rhinos were big losers at the 1994 CITES meeting. In spite of startling declines in rhino populations over the previous ten years, the CITES parties decided to consider legalizing trade in rhino horn. Furthermore, South Africa's white rhinos were taken off Appendix I (but to allow trade in the live animals, not in their horn).

Conservation efforts in several African countries may be starting to pay off.  The Black rhino increased from an estimated 2,408 in 1995 to 2,599 in 1997, and White rhinos increased from 7,563 in 1995 to about 8,466 in 1997.

Rhinos on the run

Elephants

Major problems confronting CITES have resulted from the highly lucrative trade in the ivory from tusks of elephants. In South Africa the elephant population in the last century was about 200,000 elephants, but the numbers had been reduced to 120 by 1920.  The total African elephant population suffered an extraordinary crash during the 1980's - from 1.3 million in 1979 to 625,000 in 1989, largely because of illegal poaching to satisfy the demand for ivory.  In response to these figures, CITES voted in 1989 to list the African elephant on Appendix I, which bans all trade.  Since the ban, the scientific basis of this claim has been refuted.

Sales of raw ivory and poaching dropped off considerably after the CITES listing. In the 1980's, poachers killed 3-4,000 elephants a year in Kenya, and ivory sold for $150 a pound. By 1994 the kill was down to about 50 per year, and the price to $5 a pound.  In a partial lifting of the ivory ban, Namibia and Zimbabwe were allowed to sell some of their existing ivory stockpiles to Japan in 1999.

Elephant populations have rebounded so well in several African countries (especially Kenya, with 25,000 elephants and South Africa with 11,000) that they are facing overcrowding problems. Most of the herds are in National parks with defined boundaries, and when their density reaches a certain level the damage they do to vegetation becomes unacceptable. This can have secondary effects; for example in South Africa's Kruger National Park the population was up to 11,000 in 1995, and baobab trees, an endemic lizard and an endemic chameleon are suffering because of elephant damage. In response, park managers have started to "cull" the elephant populations by shooting about 250 each year from helicopters. Attempts are being made to save these elephants from shooting, by moving them into private game reserves, and to develop contraceptive vaccines to make it possible to control their reproduction.

Since 1998 there has been a huge increase in illegal trade of elephant ivory, driven mainly by the growing economic power of consumers in China.  Kenya and India are proposing to place all African elephant populations back under Appendix I, whereas other African countries are developing ways of producing and exporting ivory under controlled conditions.

National Geographic Magazine: July 1996 @ nationalgeographic.com
Mar. 13, 1997 Testimony: Dr. Teresa M. Telecky

Primates (Monkeys, Apes and Lemurs)

This group of animals is of special concern because they are so highly evolved, vulnerable, and closely related to humans.  In addition to their intrinsic value as members of functioning, biologically rich tropical ecosystems, they are extremely valuable in our efforts to understand ourselves and are also used extensively in medical research.  But the first primate to go extinct in about three hundred years, a West African monkey called the Miss Waldron's red colobus, has been driven to extinction in the last few decades.  Scientists carried out an extremely thorough search for without finding any hint of its presence.  Biologists predict this will be followed in the next few years by many more extinctions of West African primates and other wildlife.  The animals' habitats have been greatly fragmented by logging and road building, and this has created isolated islands of habitat where the animals can easily be exterminated by hunters supplying the lucrative trade in "bush meat", which is sold to urban restaurants.  Before this case, the most recent documented primate extinctions were a small Jamaican monkey in the early 1700's, and the giant lemurs of Madagascar in the 1500's.  Other endangered primates now include lemurs in Madagascar, tamarins in Brazil, langurs in Vietnam, orangutans in Sumatra, and gorillas and a variety of monkeys in Africa.

Gorillas are being Exterminated | Species crisis

Bears

Group issues bear survival warning 

Wild Birds

Many parrots, macaws and cockatoos are also being driven close to extinction by international trade. Each year at least 8 million birds are taken from the wild for the international pet market, and the U.S. is one of the largest importers. An estimated 225,000 exotic birds are illegally imported into the U.S. every year, most of them across the Mexican border. About half of the birds die during capture and holding. The pet trade has been responsible for the serious decline of 40 species in the wild. The hyacinth macaw, the largest parrot in the world, has declined from 100,000 individuals in the wild 20 years ago to less than 3,000 today. Spix's Macaw is down to a single male in the wild. Biologists are now trying to select an eligible female from the 26 known captive birds. This lucky animal will be released into the wild near where the existing survivor lives.

Illegal Trade Eradicates Nepal's Endangered Birds

Reptiles

Asia's endangered freshwater turtles attract international aid

Sea Horses

A 1996 report by the World Wildlife Fund indicates that populations of the sea horse in the Indo-Pacific are being heavily exploited for the Asian traditional medicine market. These unusual fish are likely to suffer the same fate as most other fisheries if conservation measures are not introduced quickly. The report, for the first time, calls on the Asian traditional medicine community to support conservation measures.

CITES 1997

The member nations of CITES have periodic meetings where they can list or delist species or move species from one appendix to another. The 10th Meeting of the Conference of the Parties to CITES took place in Zimbabwe from 8-20 June, 1997.  A summary of the decisions is available.   Decisions made at this meeting with conservation votes prevailing included rejection of attempts by Japan to reopen commercial trade in whales, sea turtles, and white rhinos. The most controversial issue was the proposal by three countries (Botswana, Namibia and Zimbabwe) to downlist their elephant populations from Appendix I to II to allow for trade in stockpiled ivory to Japan, exports of sport hunting trophies, exports of live elephants, and export (for Zimbabwe) of hides and of leather goods and ivory carvings for non-commercial purposes. The U.S. opposed these proposals because of the risks posed to elephants from any resumption of the ivory trade.  The proposal was passed by the required majority, and the downlisting went into effect on Sept. 18, 1997. South Africa’s elephant population was transferred from Appendix I to Appendix II at the CITES 2000 meeting.

CITES 2000

At the 11th Conference of the Parties to CITES in Nairobi, Kenya, in April 2000, proposals were made to list whale sharks, great white sharks and basking sharks, turtles and whales.  They achieved majority support, but none could achieve the two-thirds majority necessary for adoption. 

Some CITES-listed species are now recovered enough to be delisted or downlisted to a lesser level of protection. These include the Sonoran green toad, native to Arizona and Sonora, Mexico; North American populations of the gyrfalcon, a bird of prey; and the white wicky, a plant related to mountain laurel and native to the coastal areas of North and South Carolina.

Other species are not recovering, and the U.S. is proposing stricter protections for these.  They include the Holywood lignum-vitae, a valuable timber species; the pancake tortoise, native to Kenya and Tanzania; and three species of Asian pangolins, which resemble anteaters.

Problems in Controlling International Trade 

Enforcement

International treaties like CITES do not have enforcement powers; they are implemented when a signatory nation passes laws making it a criminal act to violate them. For example, in this country the Endangered Species Act (ESA) allows the Secretary of the Interior, through the U.S. Fish and Wildlife Service, to exercise control over trade in wildlife. Under the ESA, a violation is a misdemeanor, with a maximum penalty of $20,000 and/or one year in prison.

In 1992 the United States passed the Wild Bird Conservation Act, which prohibits the import of all CITES-listed birds (almost 1,000 species) except for those included on an approved list. To support elephant conservation efforts, the United States passed the African Elephant Conservation Act in 1988. It controls import and export of raw African elephant ivory.

The Rhino and Tiger Product Labeling Act, passed by the US Congress in October 1998, will help authorities to curb trade in tiger and rhinoceros products.  The import of such products has been illegal for many years under the ESA and CITES, but they continue to be available in many US cities.  In fact, a recent study by TRAFFIC North America found that about half of the surveyed US shops selling traditional Chinese medicines were offering products made from protected species.

The main difficulty in controlling this trade under the ESA is that the law enforcement agencies have to prove that the products actually contain rhinoceros or tiger, but they do not have the forensic techniques necessary to do this. If tiger bones are ground to a powder, there is no available method to prove that it comes from tiger (it does not contain DNA).  Also, the Endangered Species Act prohibits only the import, export and interstate commerce in such products; it does not specifically prohibit their sale.

The Rhino and Tiger Product Labeling Act:

prohibits the import, export and sale of any product for human consumption or application containing, or labeled or advertised to contain, any substance derived from any species of rhinoceros or Tiger;

carries a penalty of up to six months in prison, and fines of up to US$12,000 per violation; and

provides for the development and implementation of an educational outreach program in the USA for the conservation of rhinos and tigers

Some western conservationists have attempted to discredit traditional Asian medicine and other uses of wildlife by arguing, or by using scientific studies to prove, that the substances being marketed are not effective.  Read How the Tiger Lost Its Stripes for an interesting account of this strategy and how it has usually failed.

Reservations

All seven species of sea turtle are listed on Appendix I, yet over 20,000 turtles are killed every year to satisfy the Japanese market for carved turtle shell products. This is possible because of an enormous loophole in the CITES agreements, called the "reservation". By "entering a reservation" on a species, a nation is not bound by CITES trade restrictions on that species! Japan holds reservations on twelve Appendix I species, more than any other country. Three of these are for sea turtles, most of which are exported illegally from their countries of origin. Sea turtles are also threatened by the shrimp fishery and by loss of nesting sites due to development. Japan has agreed to stop importing hawksbill turtles under the threat of a trade ban by the U.S.

Illegal Trade

Illegal wildlife trade is rampant, and is estimated to make up between a quarter and a third of the total trade in wildlife and wildlife products. Even in the U.S., with better enforcement than most countries, illegal wildlife imports amount to $100 - $250 million per year. Less than one in four of the reported shipments are inspected, and many shipments are made across the Mexican and Canadian borders without any reporting. A 1996-1997 investigation of traditional Asian medicine shops in seven North American cities (Atlanta, Los Angeles, New York, San Francisco, Seattle, Toronto, and Vancouver) showed that traditional East Asian medicines containing or claimed to contain materials from endangered or protected species (tiger, rhino, leopard musk deer, and bear) were widely available. Efforts are being made to reduce this demand in the United States, for example through the Rhino and Tiger Product Labeling Act which gives USFWS authority to take legal action against the sale of medicines made from rhino and tiger parts.

Another way that pressure can be brought to bear on offending nations is through economic sanctions. For example, in this country the Secretary of the Interior is empowered to certify any nation that jeopardizes the effectiveness of an international conservation treaty (like CITES or the International Convention for the Regulation of Whaling), and then the President can impose economic sanctions, usually restrictions on the importation of fisheries or wildlife products, on the offending nation.

In 1994 the Clinton Administration announced that it will ban the import of all wildlife products from Taiwan because of its failure to stop the use of tiger and rhino products. The ban was lifted after a year because President Clinton determined that Taiwan had taken substantial steps to halt commercial trade in these products.

Another example is Thailand, which has been charged with about 100 CITES violations since 1988. Bangkok has become an international center for illegal wildlife, and a center for "laundering" wildlife  including live cheetahs, tigers, bears, orangutans, gibbons, and siamangs to disguise their country of origin. There was also a problem with illegal imports from Thailand into the United States, including ivory jewelry, sea turtle products, leopard and tiger parts and products, and a large variety of reptile products. In response, in 1991 the U.S. banned trade with Thailand in all CITES-listed species. In November 1995, the U.S. received assurances from the government of Thailand that CITES would be effectively implemented within that country, and lifted the sanctions.

In Colombia, poachers nearly wiped out the Orinoco crocodile, the American crocodile and the black caiman, in order to illegally export thousands of hides each year in the 1980's. In 1987, the government established a licensing system, to allow crocodile farming. But these farms have been consistently used as a front for poaching operations. Poaching is still a lot less effort than breeding these animals.

Undercover inspections of retail stores in Athens, Greece in July 1998 revealed spotted cat furs, elephant ivory and Hawksbill Turtle shell as well as live animals for sale, all of which are illegal under CITES.  In response, conservationists called for a worldwide boycott on trade in wild plants and animals with Greece.

There was a huge increase in wildlife trade between Eastern Europe and Central Asia in 1990-91 after the dissolution of the Soviet Union. Several threatened species including snow leopard and Tien Shan brown bear are illegally hunted for trade, and many others are traded at unsustainable levels.

FREE TRADE AND THE ENVIRONMENT

For many years global free trade issues were negotiated through the General Agreement on Tariffs and Trade (GATT).  The Uruguay Round negotiations of GATT (1986-94) led to the formation in 1995 of a more formal and powerful body called the World Trade Organization. It has a membership of 132 countries (as of September 1997).  Its major goal is to establish “a system of rules dedicated to open, fair and undistorted competition.”

Some WTO principles:

a country should not discriminate between its own and foreign products

trade barriers should be removed through negotiation

Because of fears that free trade would lead to increased pressure on natural resources, the WTO established a Committee on Trade and the Environment.  The WTO does not want to intervene in national or international environmental policies or to set environmental standards.  But they believe that free trade is, in general, beneficial to the environment.  They argue that "Removal of trade restrictions and distortions, in particular high tariffs, tariff escalation, export restrictions, subsidies and non-tariff barriers, has the potential to yield benefits for both the multilateral trading system and the environment."

In late November, 1999, the streets of Seattle looked like a war zone because U.S. troops were brought in to control 50,000 protesters including labor and environmental groups concerned about the negative effects of free trade.  Read an analysis of the issues behind the protests by the Canadian Institute for Business and the Environment.

How Free Trade can work in favor of conservation

One way that free trade may work in favor of conservation is through the elimination of perverse subsidies (Subsidies that are adverse in the long run to both the economy and the environment).  Two major areas of perverse subsidy are:

Global subsidy of agriculture = $325 billion

For example, government subsidy of fisheries has led to overharvesting, which is (in the long term) detrimental to both the economy and the resource.

 

How Free Trade can work against conservation

Free Trade is restricting the ability of individual countries to use their trading power to protect natural resources.  Some countries (e.g. the U.S.) have enforced trade embargoes against other countries that fail to protect natural resources.  The WTO has ruled against this practice on several occasions:

U.S. embargoes invalidated by GATT / WTO
Import of non dolphin-safe tuna
Import of non-turtle-safe shrimp
Import of harp-seal fur coats

In general, WTO rulings follow the principle that environmental issues should be dealt with explicitly through multilateral agreements (e.g. CITES), not through trade manipulation.

Some WTO rulings:

The countries concerned should try to cooperate to prevent environmental damage.

The complaining country can act (e.g. on imports) to protect its own domestic environment, but it cannot discriminate against other countries.  Standards, taxes or other measures applied to imports from the other country must also apply equally to the complaining country's own products.

When the issue is not covered by an environmental agreement (e.g. CITES), WTO rules apply, including:

Trade restrictions cannot be imposed on a product purely because of the way it has been produced. 

One country cannot impose its standards on another country.

The ruling on means of production has been used to justify findings against U.S. embargoes, beginning with the Tuna-Dolphin Case:

According to the U.S. Marine Mammal Protection Act, if a country exporting tuna to the U.S. does not meet U.S. dolphin protection standards, the US government must embargo all tuna imports from that country. Following this law, exports of tuna from Mexico to the U.S. were banned. Mexico complained in 1991 under the GATT dispute settlement procedure. The GATT panel concluded that the U.S. could not embargo imports of tuna products from Mexico on the grounds that the way tuna was produced did not satisfy U.S. regulations. They ruled that one country cannot take trade action for the purpose of attempting to enforce its own domestic laws in another country - even to protect animal health or exhaustible natural resources. Similar arguments have been made in the case of the U.S. Import Embargo on Harp-Seal Fur Coats from Greenland, which was required by the Marine Mammal Protection Act.

Going against the trend, the European Union is proposing to use trade preferences to encourage developing countries to manage their forests and other natural resources in a sustainable way.

 

COMMON PATTERNS OF OVEREXPLOITATION

The history of natural resource exploitation reveals a pattern that repeats itself over and over again. Even when the exploitation is regulated, the resource very often gets depleted. Several common problems can be identified:

Oversimplified theory

Over-exploitation often occurs because ecological theory is not able to accurately predict the effects of exploitation:

Maximum sustainable yield. It is often assumed that the resource can be harvested up to a certain level without depleting it. Fruit flies in a bottle go through a typical population curve in which about half way through the growth of the population, its growth rate is maximal. So the theory is that if you harvest a population down to this level, you will keep it at that maximum growth rate and get a "maximum sustainable yield". In a wild population, this theory implies that the remaining animals after a harvest will increase their reproductive rate to compensate. Management of whales and fish have usually been based on the concept of maximum sustainable yield, even though the resource managers never had any evidence that natural populations behaved this way. This management procedure failed repeatedly, leading to the depletion of many stocks of whales and fish.

Competition. An alternative model is that when you deplete one resource, the increased availability of food and other requirements cause competing species to increase their populations. Perhaps, for example, blue whale populations were slow to recover from whaling because other whales, that also feed on krill, increased their numbers while the blues were getting depleted. The whalers are now trying to use this argument to justify harvesting Minke whales, which need the same food as the much more endangered blue whale. They argue that harvesting the Minke whales will indirectly benefit the Blue whale. Similarly, elephant hunters are arguing, that if the elephant population is allowed to recover, they will compete for food with other endangered herbivores such as impala, giraffe, kudu, and many others.

Natural variability and oscillations mask the effects of overexploitation. Depletion is often blamed on "natural cycles" when it might be due to over exploitation.

Natural variations do occur; one of the best documented examples is in populations of hare (jackrabbit) and lynx (cat). In an exploited population, such cycles can cause a "ratchet" effect: Industry (and government) will rapidly invest (and therefore increase exploitation) during periods of abundance, but will be reluctant to disinvest (or lower exploitation rate) during periods of scarcity.
External Factors.  External factors combine with overexploitation to cause depletion. The El Niño climatic condition (with higher surface water temperatures) of 1972 combined with overfishing to wipe out the Peruvian anchovy fishery in the early 1970's. Habitat loss, pollution, and introduction of exotic species can also contribute to loss of the exploited species.

Economics

Short-term gain.  The desire for profit in the short term is always greater than the desire for sustainable exploitation. This is often exacerbated by competition for the resource. If you don't harvest it, someone else will. It is usually assumed that the resource is abundant elsewhere (the "Tragedy of the Commons" - learn about it by playing The Tragedy of the Commons Game).

The Center for Private Conservation believes that the only way to prevent the Tragedy of the Commons is to bring natural resources into private ownership.  They argue, for example, that salmon stocks in the U.S. have been wiped out because they are in public ownership, whereas in some European countries the salmon has been conserved because the rights to the fish or to the river are privately owned.  What do you think?

Increase in Value.  As the resource gets rarer, its value increases (e.g. $67,000 tuna, etc.). This increases the hunting pressure.

Perverse Subsidies.  When the resource is so depleted that it is uneconomic to harvest it, government will often subsidize the industry in order to delay unemployment (e.g. below-cost timber sales; export subsidies). The effect of the subsidy is to encourage more overexploitation.

Enforcement problems

Poaching. Managing wildlife has often been frustrated by poaching (illegal hunting) and illegal marketing. We already talked about several examples of this.  In the U.S., poaching is organized, heavily commercialized and may be second only to the drug trade in size and deadliness.

IS SUSTAINABLE USE A VIABLE CONSERVATION STRATEGY?

It is often argued that the profit coming from sustainable use of wildlife species provides a strong incentive for conserving the species, and that harvesting, even of endangered species, should be allowed for this reason.  Unfortunately, as we have seen, there are many examples where this has not worked.  But there are some examples where it seems to be working. Crocodiles in Australia, and Vicunas in South America, are being harvested in a controlled manner so that their populations are sustainable or even increasing.  But the successful examples are mainly those where the species has become domesticated.  They are examples of successful farming rather than sustainable wildlife exploitation.