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Chapter 15 Biodiversity and Conservation Biology
Saving the Siberian Tiger
Up until the past 200 years, tigers roamed widely across the Asian continent, but people have driven these cats from most of their historic range, 1 and today tigers are exceedingly rare and are creeping toward extinction.
The subspecies known as the Siberian (or Amur) tiger are the largest cats in the world, with males reaching 800 lbs and 12 feet long. Siberian tigers find their last refuge in the temperate forests and taiga of the remote Sikhote-Alin Mountains of the Russian Far East.
For thousands of years the Siberian tiger coexisted with the native people, and it was uncommon for indigenous people of the region to kill a tiger.
The Russians who moved into the region in the early to mid-20th century hunted the tiger for sport and hides, and some Russians killed as many as 10 tigers in a single hunt.
Poachers killed tigers to sell their body parts for traditional medicine and aphrodisiacs to Asian countries, and road building, logging, and agriculture fragmented the tiger's habitat and provided easy access for hunters. The tiger population had dipped to 20-30 animals when international conservation groups launched a Russian-American effort, the Siberian Tiger Project, which studies and protects the tiger and educates people about tigers.
Due to various conservation efforts, today the Siberian tiger population numbers 150-450 individuals, and 500 more survive in zoos around the world.
Our Planet of Life
Growing human population and resource consumption are putting great pressure on the flora and fauna of the planet, from tigers to tiger beetles. Earth's diversity of life makes our planet unique in the universe, but we have already begun losing the very thing that makes our planet so special. Biodiversity is the sum total of all organisms in an area, and includes diversity of species, their genes, populations, and communities.
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What is biodiversity?
Dr. Edward O. Wilson defines biodiversity as the variety of organisms at all levels, from genetic variants in the same species through genera, families, and ecosystems;
The UN Environment Programme (UNEP) defines biodiversity simply as "the variety of life in all its forms, levels, and combinations." Although there are multitudinous definitions of biodiversity, it is clear that biodiversity is not simply a count of species, but a multifaceted concept.
Biodiversity encompasses several levels of life's organization
The easiest and most commonly used definition of biodiversity is species diversity.
Species Diversity.
Species diversity is expressed in terms of the number of species in the world or in a particular region.
A species is a population or group of populations whose members share certain unique characteristics and can freely breed with one another and produce fertile offspring.
Speciation, the generation of new species, adds to species diversity, whereas extinction decreases species diversity.
Biodiversity exists in subspecies, populations of a species that occur in different geographic areas and differ from one another in at least some characteristics. Subspecies occur where divergence has not proceeded all the way to speciation.
Genetic Diversity Genetic diversity encompasses the differences in DNA composition among individuals within a given species.
As a species becomes adapted to the local environment, its genetic diversity may decrease, because as long as environmental conditions remain the same the species survives better.
However, species with more genetic diversity have better chances of persisting, because their built-in variation allows them to cope with environ- mental change.
Species with little genetic diversity are vulnerable to environmental change or diseases for which they are not genetically prepared.
Species with low genetic diversity may also suffer the effects of inbreeding, whereby genetically similar individuals mate and produce weak or defective offspring.
Scientists are concerned over low genetic diversity in species with low population sizes, including cheetahs, bison, and elephant seals.
Ecosystem diversity Biodiversity at this level includes groupings of organisms, their interactions with one another, and their relationships with their abiotic environment. Ecosystem diversity refers to the number and variety of ecosystems in an area; community diversity refers to the number and variety of community types; and habitat diversity refers to the number and variety of habitats.
Landscape diversity refers to the variety and geographic arrangement of . habitats, communities, or ecosystems over a wide area, including the sizes, shapes, and interconnectedness of patches.
Measuring biodiversity is not easy
Species diversity is a good gauge for overall biodiversity when comparing different areas, but we still are profoundly ignorant of the number of species that exist.
Scientists have identified approximately 1.75 million species, but there may actually be about 14 million species.
Insects account for more than half of all species in the world, and about 40% of all insects are beetles.
There are several reasons why we don't know the exact number of species on Earth.
Some areas of Earth, such as the ocean depths, hydrothermal vents, and the tree canopies and soils of tropical forests, have not yet been completely explored.
Many species are tiny and easily overlooked, such as bacteria, roundworms, and soil-dwelling arthropods.
Finally, one species can turn out to be two or more once biologists look more closely, which happens even with large species such as trees, birds, and whales.
In 2000, the All Species Foundation was created "to discover and describe all living organisms on Earth within one human generation, and to make this information available to everyone everywhere" and is backed by 100 collaborating scientists.
You may be able to help measure biodiversity near where you live
Today, more and more locally based efforts are springing up to measure biodiversity in small, commonplace areas.
In a "bioblitz," taxonomists and interested citizens team up and race to thoroughly survey every species they can find within 24 hours in a state park or a city. Bioblitzes promote public awareness of biodiversity as well as obtain accurate species counts, yet they can also result in the discovery of new species.
Global biodiversity is not distributed evenly
Species are not distributed across the planet evenly, and scientists have tried to explain the distribution of biodiversity.
One group may have only one or a few species, while another group, such as the family that contains daisies, ragweed, and sunflowers, may have thousands of species.
Adaptive radiation occurs when an ancestral species gives rise to many species that fill different niches, and each species adapts to its niche by natural selection.
Species richness also varies according to biome, and tends to increase as one approaches the equator, so that tropical dry forests and rainforests support more species than do tundra and deserts.
This pattern or variation with latitude, or latitudinal gradient, is probably due to increased plant productivity and climate stability at tropical latitudes. Stable climates, with similar daily temperatures and rainfall, allow species to co-exist and fill specialized niches.
Polar and temperate regions may have fewer species because glaciation could have forced species to move toward more tropical latitudes.
Biodiversity Loss and Species Extinction
Humans are causing the loss of all levels of biodiversity through the extinction of species.
Extinction occurs when the last member of a species dies, and the species ceases to exist, while extirpation is the extinction of a particular population from a given area (but not the entire species globally).
Extinction is "natural"
Scientists estimate that roughly 99% of all species that have ever lived are already extinct.
Before humans, most extinctions occurred one by one; this background rate of extinction caused one species of bird (or mammal) to became extinct every 500-1,000 years.
Earth has experienced five previous mass extinction episodes.
Extinction rates have surpassed this background rate during five mass extinction events during Earth's history; each event took more than 20% of life's families and at least half its species.
The most severe episode was that at the end of the Permian period (248 million years ago), when 90% of all species vanished.
The most well-known episode was at the end of the Cretaceous period, 65 million years ago, when an asteroid impact killed off the dinosaurs.
The modern era, called the Quaternary period, may see the extinction of more than half of all species, but today's ongoing mass extinction is different in two primary respects: first, humans are causing it, and second, humans will suffer as a result of it.
Humans set the sixth mass extinction in motion years ago
There are many instances of human-induced species extinction over the past few hundred years, including those of the dodo, passenger pigeon, Carolina parakeet, great auk, and Labrador duck; several more species, like the whooping crane, California condor, and Kirtland's warbler, teeter on the brink of extinction.
Human-caused extinction is nothing new: Thousands of years ago, waves of extinctions occurred wherever people colonized new areas, from Hawaii to Australia.
Current extinction rates are much higher than normal
As our population and resource consumption strain habitats and wildlife, species are lost at a faster pace.
The world's leading scientists report that current global extinction rates are more than 1,000 times greater than they would be without human destruction of habitat.
More than 30,000 plant and animal species face extinction; mammals are becoming extinct 40 times faster than ever before and 45% of Earth's forests, 50% of its mangrove ecosystems, and 10% of its coral reefs have been destroyed.
The World Conservation Union's (IUCN) Red List, a list of species facing unusually high risks of extinction, reported that 24% of mammal species and 12% of bird species are threatened with extinction.
From 1996 to 2002 the total number of threatened vertebrate animals climbed by 6%, and the actual numbers of species extinct and threatened are greater than the known numbers.
The major causes of species loss spell "HIPPO"
HIPPO denotes the five primary causes of species decline and extinction: Habitat alteration, Invasive species, Pollution, Population, and Overexploitation.
The most prevalent and powerful of these five causes is habitat alteration.
Habitat alteration: Nearly every human activity-including farming, grazing, deforestation, urban sprawl, and global climate change-alters the habitat of organisms. Any change, including degradation or destruction, of a habitat is likely to make the habitat less suitable for organisms because they are adapted to the original habitat.
Human-induced habitat change may benefit species like starlings, house sparrows, pigeons, and gray squirrels that do well in urban environments because they are weedy, cosmopolitan species that are in little danger of disappearing.
Habitat alteration is the primary source of population declines for 83% of threatened mammals and 85% of threatened birds.
Invasive species: The introduction of invasive species to new environments has also pushed native species toward extinction.
Accidental introductions include marine organisms in the ballast water of ships, escaped pets, or the weed seeds that stick to our socks when we travel.
Humans who intentionally introduced species to new places for food, or for economic or aesthetic reasons, were usually unaware of the ecological consequences that could result.
If organisms in a new area are released from the limiting factors of their native parasites, predators, or competition, they can increase rapidly and displace native species.
Invasive species also cause billions of dollars in economic damage each year.
Island species are especially vulnerable to invasive species, because they have been isolated for so long that they have not evolved the defenses to resist invaders.
Pollution: Air pollution can degrade forest ecosystems; water pollution can affect fish and amphibians; and agricultural runoff can harm terrestrial and aquatic species.
Although pollution is a substantial threat, it is less significant than the public thinks, and is less of a threat than are habitat alteration, invasive species, or human population growth
Population growth: The increasing human population intensifies every environmental problem and poses an indirect threat to other species through each of the other components of the HIPPO dilemma.
Along with the increasing resource consumption, human population growth is the ultimate reason behind many of the threats to biodiversity. Overexploitation This term refers to two different things: overharvesting of species from the wild and overconsumption of resources by people.
For some species, hunting by humans poses a threat of extinction (e.g., the Siberian tiger) because the species is large, few in number, long-lived, and raises few young-a classic K-strategist.
Many other K-strategist animals, such as whales, gorillas, and sharks, are killed each year.
Sometimes causes of biodiversity loss are difficult to determine
The reasons for a species' decline can be multifaceted, complex, and hard to determine.
For example, frogs, toads, and salamanders worldwide are decreasing and several species have gone extinct due to a wide array of factors, including chemical contamination, disease transmission, habitat loss, ozone depletion, and climate change.
Benefits of Biodiversity
Biodiversity is being lost at all scales, but many people question whether extinction of species is important.
There are a number of concrete reasons for preserving biodiversity, showing how biodiversity directly or indirectly supports the long-term sustain- ability of human society.
In addition, many people feel that there are ethical and aesthetic dimensions to biodiversity preservation that cannot be ignored.
Biodiversity provides valuable ecosystem services free of charge
The valuable processes that intact ecosystems provide free of charge are known as ecosystem services, including cleaning air and buffeting aquatic systems against flooding and drought.
Native races of crops can provide insurance against disease and drought, while abundant wildlife can attract tourists and boost economies of developing nations.
Biodiversity maintains free ecosystem services by: providing food, fuel, and building materials, purifying and detoxifying areas, moderating droughts, winds, and climate, renewing soils, pollinating plants, controlling pests, and maintaining genetic diversity.
Additionally, biodiversity provides cultural and aesthetic benefits to people, and gives organisms the ability to adapt to changes in the environment.
If humans had to pay for these services, the value of just 17 of these ecosystem services would be $16-54 trillion per year.
Although people may understand that biodiversity provides free services, skeptics ask whether the loss of a few species makes a difference in an ecosystem's ability to function.
Top predators play key roles in their ecosystems
Removing a species that can be replaced by others may make little difference, but removing a keystone species can significantly change an ecological system.
Removing a single individual at the top or a food chain can have impacts that multiply as they cascade down the food chain, and any changes to the plant community may have effects that work their way back up the food chain.
Top predators are very vulnerable to human impacts, because people kill them for meat, or think they pose a danger to humans or livestock.
Top predators also need large areas of habitat, making them especially vulnerable to habitat loss and habitat fragmentation.
In addition to being vulnerable to toxic pollutants through biomagnification, top predators are K -strategists, living long lives and producing few offspring, so removing even a few individuals can make a big difference in the species' survival.
Because environmental systems are complex, and it can be hard to predict which species may be important to an ecosystem's functioning, Aldo Leopold advised that "to keep every cog and wheel is the first precaution of intelligent tinkering:'
Biodiversity gives us natural classrooms
Ecologists need undisturbed, natural areas to understand human impacts; biodiversity enables parks and reserves to serve as natural classrooms.
These areas provide a wide array of tangible educational and social benefits, including the study of biology, natural history, ecology, chemistry, painting, and photography.
Biodiversity enhances food security
Biodiversity benefits agriculture by preserving the genetic diversity within crop species and their ancestors. .
Wild crop strains provide disease resistance worth billions of dollars; for example, Turkey's wheat crops received $50 billion worth of disease resistance from wild strains.
Other species can serve as potentially important food crops) such as the babassu palm of the Amazon that produces more vegetable oil than any other plant, or the serendipity berry that produces a sweetener 3,000 times sweeter than sucrose.
Biodiversity provides traditional medicines and high-tech pharmaceutical products
Wild species yield new products, including pharmaceuticals, fibers, crops, and petroleum substitutes.
Many of today's drugs and medicines were discovered by studying chemical compounds present in wild plants, animals, and microorganisms.
In 1997, 10 of the 25 best-selling pharmaceuticals, worth $75-100 billion, came from wild species; for example, aspirin comes from the meadow-sweet plant.
Over 75% of the world's people use biological resources in traditional medicine.
Scientists have discovered treatments for cancer, stomach disorders, motion sickness, and leukemia in organisms.
One compound had the potential to treat gastric ulcers, but the species of frog that provided this compound is now extinct.
Biodiversity provides economic benefits through tourism and recreation
Undisturbed biodiversity can provide income through tourism, particularly in developing tropical countries with high species diversity and beautiful landscapes.
Visitors to protected natural areas spend money at local businesses, hire local people as guides, and support the parks that employ local residents. The United States benefits from ecotourism from its national parks that draw millions of visitors domestically and from around the world.
Ecotourism serves as a powerful incentive for nations, states, and local communities to preserve natural areas and reduce impacts on the landscape and native species. However, as ecotourism increases, too many visitors to natural areas can degrade the outdoor experience and disturb wildlife.
Ecotourism's effects on species are much debated and vary enormously, depending on the species in question.
People value and seek out connections with nature
A deeper reason for biodiversity's importance is a phenomenon called biophilia, "the connections that human beings subconsciously seek with the rest of life."
Evidence for biophilia exists in people's affinity for parks and wildlife, keeping of pets, the high value of real estate with a view of natural landscapes, and our interest in hiking, bird watching, fishing, hunting, backpacking, and other outdoor pursuits.
Do we have an ethical responsibility to prevent species extinction?
As more and more people take up biocentric or ecocentric worldviews, they feel that other organisms have an inherent right to exist.
Although humans must use resources to survive, we have conscious reasoning ability and are able to control our actions and choose what we do.
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Aldo Leopold's land ethic argues for protecting other species, as he argues that humans and "the land" (this term preceded "biodiversity") were members of the same community and so humans have an ethical responsibility to them.
Because our ethical sense has developed from our intelligence and ability to choose, we must include ethical considerations when we decide how to address biodiversity loss.
Despite all the reasons to preserve biodiversity, its future is far from secure, and even our protected areas and national parks are not big enough or well enough protected to safeguard biodiversity.
Conservation Biology: The Search for Solutions
People since the time of Aristotle have worried about habitat and wildlife destruction.
Conservationist and preservationist ethics in the United States inspired some of the first parks and protected areas.
More and more people feel that something must be done to stem the loss of biodiversity, and as E. O. Wilson wrote: "Troubled by what we have wrought, we have begun to turn in our role from local conqueror to global steward."
Conservation biology arose in response to increasing extinction rates
Conservation biology is a scientific discipline devoted to understanding the factors, forces, and processes that influence the loss, protection, and restoration of biological diversity within and among ecosystems.
Conservation biology developed out of scientists' alarm at biodiversity losses and the degradation of the natural systems they had spent their lives studying.
Because conservation biologists try to solve problems, certain values and ethical standards are implicit in this discipline.
Some scientists view conservation biology as an integration of science and activism, while others see it as an applied and goal-oriented science.
But as scientists recognize the human impacts on the planet, they want
their own work to address environmental problems, and the reputation of conservation biology has risen.
Conservation biologists integrate evolution and extinction with ecology and the dynamic nature of environmental systems to study the impacts of humans on other organisms and design ways to reduce these impacts.
Island biogeography theory is a key component of conservation biology
The equilibrium theory of island biogeography was first applied to oceanic islands to explain how species come to be distributed among them.
Researchers apply this theory to other types of islands, including islands of habitat-patches of one type of habitat isolated within vast "seas" of others.
Siberian tigers exist in a habitat island-a mountain range isolated from others by topography, logged forests, and oceans, and surrounded by low- lands densely populated with people.
Island biogeography theory predicts the number of species on an island based on the island's size and distance from the mainland.
The number of species on an island is a balance between the number of species being added by immigration and the number being lost through extinction.
The area effect hypothesizes that as an island increases in size, the number of species on the island increases.
Immigration rates are greater for islands with few species while extinction rates are greater for islands with many species (because competition between species keeps the numbers of individuals small).
Larger islands possess more species because more space allows for larger populations, which are less vulnerable to extirpation.
More species will arrive at a large island in the first place because they present fatter targets for wandering organisms to encounter.
Larger islands may also possess more habitats than smaller islands, pro- viding suitable environments for a wider variety of species.
Because of the distance effect, the farther an island is from a continent or a source of immigrants, the fewer species will be living on the island.
Remote islands are more difficult for individuals to reach, so the distance between an island and the nearest continent also affects species number on the island.
Terrestrial habitat islands, such as fragmented forests, also show these pat- terns; small forest islands lose their diversity fastest, starting with those large species that were few in number to begin with.
Some species act as "umbrellas"
Animals like tigers that need large amounts of land are called umbrella species, because if we protect the spacious habitat the species needs, we will also be safeguarding the habitat needed by many other species.
Large charismatic animals are excellent tools for conservation, because they are ecologically important as keystone species, and meeting their habitat needs automatically helps meet those of thousands of less charismatic animals, plants, and fungi.
Symbols of wildlife, such as the World Wildlife Fund's panda, illustrate how a large, cute, endangered animal requiring sizeable stands of undisturbed habitat can become a public favorite and an effective tool for solic iting money for conservation efforts that protect much more than just that organism.
Should endangered species be the focus of conservation efforts?
The Endangered Species Act (ESA)(1973), the primary legislation for protecting biodiversity in the United States, forbids the government and private citizens from destroying endangered species or their habitats, and also forbids trade in products made from endangered species.
The ESA's aim is to prevent extinctions, stabilize declining populations, and enable populations to recover to the point that they no longer need protection.
As of 2003 there were 1,263 species in the United States listed as "endangered" or as "threatened:' the status one notch less severe than endangered. The ESA succeeded in helping species (such as the bald eagle} recover, and in stabilizing about 40% of the declining populations in spite of continued habitat degradation.
Unfortunately, the agencies responsible for enforcing the ESA, the U.S. Fish and Wildlife Service and the National Marine Fisheries Service, have faced budgetary shortfalls.
Not all citizens support endangered species protection, and efforts to reauthorize the ESA were opposed in the U.S; Congress in the late 1990s and early 21st century.
Some people think that the ESA focuses only on single species, and values the life of an endangered species over the life or livelihood of a human.
Opposing the ESA's protection of a species becomes harder if one accepts that what's really at stake is the community, of which this umbrella species is a part.
Most people who resent the ESA do so because they worry that federal officials will restrict the use of private land if threatened or endangered species are found on it, so people believe in the philosophy of "shoot, shovel, and shut up."
However, provisions of the Act protect landowners through habitat conservation plans and safe harbor agreements that allow landowners to harm species in some ways if they voluntarily improve habitat for them in others. In Canada's Species at Risk Act (SARA), the government stressed the approach of cooperation with landowners and provincial governments, rather than presenting the law as a decree from the national government.
Environmentalists and many scientists protested that the act was too weak and failed to protect habitat adequately.
Can captive breeding, reintroduction efforts, or cloning help save endangered species?
Zoos and botanical gardens conduct captive breeding of endangered species, so that large numbers of individuals can be raised and then reintroduced into the wild.
For example, the United States started an extensive program to save the California condor, because by 1982 only 22 condors remained.
Biologists trapped all birds and took them into captivity, and bred them so the offspring could be released; in recent years, many adults and young birds have been released into the wild at sites in California and Arizona. In 2003, one nesting pair raised the first condor chick in the wild since 1984.
A reintroduction program for wolves in Yellowstone National Park, Arizona, and New Mexico has been resisted by ranchers, who fear the wolves will attack livestock and therefore shoot the wolves.
A new idea is to save the DNA of endangered species and clone them in the future, but most biologists feel that without habitat and protection in the wild, having a cloned animal in a zoo does little good.
Cloning species may actually harm preservation efforts, because it may distract people from the measures that need to be taken to prevent species extinction in the first place.
International conservation efforts include widely signed treaties
On the international level, treaties facilitated by the United Nations serve to help protect endangered species, but only if participating countries choose to enforce them.
The 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) prohibits the international transport of endangered species' body parts.
In 1992, the leaders of many nations agreed to the Convention on Biological Diversity, a treaty outlining the importance of conserving biodiversity. The Convention has three goals: {1) conserve biodiversity; (2) use biodiversity in a sustainable manner; and (3) ensure the fair distribution of biodiversity's benefits.
The Convention addresses a number of topics, such as providing incentives, managing resources, transferring technology, promoting cooperation and education, providing funding, and encouraging each nation to report its conservation efforts.
There have been successful conservation efforts around the world, from Uganda to Costa Rica, that have helped biodiversity and native peoples. Although 188 nations have signed on to the Convention on Biological Diversity, the United States joins Somalia, the Vatican, and Iraq in not joining the Convention.
For a variety of reasons, the U.S. government is no longer regarded as a leader in biodiversity conservation efforts.
Nongovernmental organizations also play a role
A number of U.S.-based conservation organizations have taken leadership roles in biodiversity conservation.
These nongovernmental organizations (NGOs) include groups like the Wildlife Conservation Society, World Wide Fund for Nature, Conservation International, World Wildlife Fund-U.S., and The Nature Conservancy. These organizations involve local people in conservation planning and implementation, buy habitat, train park managers, promote education, and develop innovative approaches to conservation.
Various other countries have also taken steps to protect biodiversity within their borders, such as the Russian government's "Decree 795" that created a Siberian tiger conservation program and declared the tiger an important natural and national treasure.
Some biodiversity conservation efforts are focused on whole communities and landscapes, such as The Wildlands Project, which is an ambitious effort to restore huge amounts of North America's land to its pre-settlement state.
Biodiversity hotspots pinpoint areas of high diversity
One effort that focuses on geographic regions, instead of single species, is mapping biodiversity hotspots to prioritize areas that support a great diversity of species and are most in need of conservation.
Hotspots not only have great biodiversity, but contain species that are endemic to the area; that is, found nowhere else in the world.
To qualify as a hotspot, a location must: (1) harbor at least 1,500 endemic plant species; (2) have suffered extensive habitat alteration or other human impact; (3) have already lost 70% of its original habitat.
The 25 ‘biodiversity hotspots’ cover only 1.4% of the planet's land surface, but house 44% of all plant species and 35% of all terrestrial vertebrate species.
Conservation efforts in hotspots protect the most species with the least amount of effort, and would need a one-time investment of $24 billion. This money represents a large bang for the buck, because the total is less than 0.1 % of the gross world product and 0.1 % of the value of the areas' ecosystem services.
Further innovative strategies are being employed
An innovative strategy for conservation is the debt-for-nature swap, in which an NGO raises money to payoff a portion of a developing country's international debt in exchange for a promise by the recipient country to set aside reserves, fund environmental education, and better manage protected areas.
Another strategy is the idea of the conservation concession, in which conservation organizations pay nations to conserve their resources instead of selling them to corporations.
The nation invests the money in a foundation that supplies the country with income each year, and keeps its natural resources intact.
