Environmental Indicators

Environmental scientists would learn very little about habitat and diversity by monitoring crows or other generalists. Specialists, however, often fluctuate in numbers in response to changes in the environment. For this reason many specialists are called indicator species because they react dramatically to changes in the environment and so serve as early warnings of environmental decay. The following table lists some indicator species and the information they provide in environmental science.

Like a canary carried into a mine to detect deadly gases, birds serve as harbingers of danger in the environment before humans sense it. Certain species require very specific habitats, so monitoring them is the best way to monitor that habitat, whether it is a wetland, beach, riparian area, woodland, or forest. Birds therefore serve as excellent biodiversity indicators for the following reasons:

» live in every climate and biome

» participate in almost every terrestrial and aquatic ecosystem on the earth

» migrate between climates and biomes

» respond quickly to changes in habitat

» easy to track and count

» give behavioral clues to threats

» most species play a central role in numerous food webs

» different species depend on certain terrestrial plants, aquatic grasses, trees, seeds, insects, rodents and other mammals, and marine species as food

» reproduction is sensitive to pollution

Source of Information : Green Technology Biodiversity (2010)


Environmental Ethics

Earliest human society consisted of hunter-gatherers in which members of a settlement ventured afield to collect plants and fruits, to fish, and to hunt meat-producing animals. In these societies, humans behaved as predators in a sustainable manner, meaning they hunted to sustain their village but they did not decimate wildlife populations.

Today Earth approaches 7 billion people, which is beyond its carrying capacity. Population densities in Africa, Asia, and South America have forced some people into a far more menacing predator role in which wildlife numbers and habitat disappear in the face of human activities. Environmental ethicists have confronted the underlying cause of this problem: poverty. The International Union for Conservation of Nature (IUCN) and the European Commission published this viewpoint in an undated briefing titled Biodiversity in Development: The Links between Biodiversity and Poverty: “Poor people themselves are often the cause of biodiversity degradation and loss, especially if lack of income alternatives drives them to over-exploit the resources.” This statement emphasizes the complex association between human poverty and biodiversity.

Environmental ethics involves the search for a solution for two opposing needs: human hunger and wildlife survival. Many African communities depend on their native wildlife for food (called bushmeat) and for income. On a small scale this practice was at one time sustainable, but an increased demand for food and space far exceeds the capacity of wildlife populations to keep up. Threats to the survival of African wildlife now include the following: people hunting for food, destruction of habitat for agriculture or urban development, disappearance of prey animals, retaliatory or preventive killings to protect villages from predator animals, and illegal wildlife smuggling and poaching for income. Some residents sell their native animals as sources for medical drugs, nonmedical cures and supplements, aphrodisiacs, religious and ornamental items, and exotic foods. Wildlife protections exist in many nations but, unfortunately, as governments strengthen the protections, black-market prices for animal products soar. As a result, the extinction of some animals hastens rather than slows.

These forms of legal and illegal hunting have been driven by hunger. Starvation is an immediate crisis for people in many regions of the world in addition to Africa, and things like bushmeat often provide a family with its only protein source. So a need to protect endangered wildlife faces another equally critical need: preventing human starvation.

Some corners of the world rich in biodiversity have revised their relationship with native endangered wildlife. For instance, hunters in Thailand and Costa Rica refrain from capturing rare birds, reptiles, amphibians, or fish because they can make more money keeping them alive (instrumental value) for ecotourism. These two countries now earn more from ecotourism than they would by destroying animal habitats.

Ethicists must also consider conflicts between biodiversity and cultural needs that may not have an obvious instrumental value. The black rhinoceros’s habitat in sub-Saharan Africa has stayed about the same size in the past 30 years, yet 90 percent of the animals have disappeared. Two related factors have contributed to this tragedy: a black market that deals in rhino horns and petroleum. In Yemen, young men earn daggers with elegantly carved handles made from rhino horn as a symbol of status and wealth. As oil-rich Yemen’s wealth has grown in the past few decades, the country has become the world’s largest importer of black rhino horn to make these ceremonial pieces. The Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) has put a global ban on the import of black rhino horn, but as a result the black market for rhino horn has flourished. Armed guards now protect many rhinoceros herds against poaching, and conservationists have even resorted to tranquilizing the animals and cutting off their horns to dissuade poachers. The dehorned animals confront another problem: adults use their horns to establish herd hierarchies and to protect their young. As with most ethical dilemmas, more than one aspect exists to each problem.

In 2005 conservationist Adam Oswell said in a radio interview in Australia, “In countries where people don’t make a lot of money, they’re not concerned about killing animals; they just want to feed their family and make money.” The link between poverty and biodiversity cannot be explained any better.

Source of Information : Green Technology Biodiversity (2010)


Gene Pools and Niches

A gene pool is the collection of all the genes in a particular population of individuals. Genetic diversity enhances biodiversity overall by improving the traits carried in a species’ gene pool. Therefore today’s biodiversity programs rely on the knowledge gained from genetic studies.

Genes control the traits of every plant and animal, and each generation transfers its genes to the next through asexual or sexual reproduction. Sexual reproduction gives an advantage to organisms because it creates more diversity in their gene pool by combining the traits from two unrelated parents. A greater variety of potential parents and greater variety of pairings in a breeding season therefore increase genetic diversity in offspring. Over time an animal population acquires advantages for survival in two ways: variations in its gene pool and random gene mutations. Even a minute change in an individual’s genes might give an animal a better chance of adapting to environmental change. Within a few generations, the advantageous gene has been passed on to many of the group’s offspring. For example, peppered moth populations living in London, England, changed their coloration during the 1950s from light gray to sooty black. The reason? Each generation of moths had gained genes for dark color so that the moths could blend into a landscape marred by pollution, smoke, and dark soot. This process increased the moths’ fitness, a species’ ability to sustain health and reproduce in its environment. Small genetic changes that enhance fitness in any specific population—London moths compared with the same species in Liverpool—over a few generations is called microevolution.

Animals evolve to meet changes in their environment by acquiring adaptations, and these adaptations may also determine a species’ role in an ecosystem. This role of a species within an ecosystem is called an ecological niche, or simply niche. Students often assume that to “occupy a niche” means an animal occupies a specific location. This is actually the definition for habitat; a niche is a species’ lifestyle or role in that habitat.

To occupy a niche, a species depends on certain foods, plants, and physical and chemical conditions within its ecosystem. Fundamental niche refers to the combination of potential physical, chemical, and biological factors that animal species use for survival. The concept of potential is important in this definition, especially when many niches overlap. Earth’s species have evolved to occupy fundamental niches that eliminate competitions, but when a species occupies a niche that overlaps with another species’ niche, it has two choices for survival: compete or adapt.

Competing directly with another species may increase the number of deaths in both species’ populations, so for the benefit of both, species often adapt to avoid competition. When different animal species adapt in this way, they are said to occupy a realized niche, a specialized portion of the fundamental niche. For example, elks in North America digest woody plants that grow on high mountain slopes, as well as plants that grow on flat lowlands. Elks are therefore capable of occupying a fundamental niche as a general grazer. Wolves have evolved to hunt elk on flat terrain to make the best use of the pack’s ability to chase a herd and separate out a single individual. Elk therefore increase their survival chances by spending as much time as they can (other than to find water) on mountain slopes,

where wolves tend not to hunt. They therefore occupy a realized niche, that of high-slope grazer of woody plants. Wolves benefit too because they conserve the energy it would take to chase elk over mountainous terrain. The wolves can carry out more successful hunts by targeting elk herds that descend for water.

North American elk make a behavioral change to occupy a realized niche, but other animals undergo a physical adaptation to accomplish the same thing. For example, two lizard species may look and act similarly and both may prefer to feed on the same types of insects. In the same habitat these species would compete directly for the same food, but through microevolution one species becomes slightly larger than the other. The larger variety of lizard ingests larger insects and leaves the tiny meals for the smaller lizard. Rather than compete, each lizard conserves its energy by feeding differently instead of competing. This behavior is called niche differentiation, or niche splitting, and it occurs only between two similar species.

How do niches affect biodiversity? The more specialized the niche, the more vulnerable an animal is to change in its habitat. Conversely, the best survivors, called generalists, thrive in broad niches; that is, they survive on many different types of food and tolerate a wide range of environmental conditions: crows, coyotes, cockroaches, and humans live as generalists. The “Case Study: The March of the Argentine Ants” gives an example of what happens when a generalist invades a habitat. Specialists, by contrast, are not as versatile and occupy narrow niches. Specialists tend to live in only one type of habitat, on a single type of food, or in a narrow range of environmental conditions. The northern spotted owl, discussed earlier, occupies a narrow niche. Other examples of specialists are giant pandas, polar bears, tiger salamanders, and red-cockaded woodpeckers. The woodpecker illustrates the precarious lifestyle of some specialists. This bird nests by carving holes only in longleaf pines that are at least 70 years old. Old longleaf pines have become limited to the southeastern coastal plain of the United States from the Carolinas to Louisiana. If the remaining longleaf pine forests disappear, the woodpecker will disappear, too. Meanwhile birds of the family Corvidae, more commonly known as crows, are generalists with no such restrictions. Crows range to just about every landmass on Earth and eat—with only slight exaggeration—anything in sight!

Source of Information : Green Technology Biodiversity (2010)


Keystone Species

Keystone species, by their natural behavior, determine the condition of other species in an ecosystem. If keystone species decline or go extinct, an entire ecosystem may not survive. Wilson has suggested with other ecologists that past extinctions were very likely due to the decline of certain keystone species that, in turn, caused ecosystem imbalance. Ecosystem imbalance occurs when one or more components disappear, putting stress on the remaining members of the ecosystem.

Sea otters and bees are but two examples of the many keystone species found in ecosystems. Sea otters’ main food is sea urchins. By holding sea urchin populations in check, otters keep them from devouring kelp forests and seaweeds that are home to hundreds of types of fish, perhaps thousands of species overall. Bees benefit ecosystems by pollinating plants and trees, which provide protective cover for other plants and habitat for insects. The insects then serve as a food source for many bird species, upon which foxes feed, upon which raptors feed.

Foundation species play a slightly different role from keystones. They change habitat in a way that enhances it for other species. African elephants play the role of foundation species through their feeding activities in which they crack and uproot trees, which helps open up areas of land and aerates soil. This condition promotes the growth of grasses for grazing animals, and eventually small bushes and woodlands follow the grasslands. The new vegetation favors tree grazers, insects, birds, and the predators that hunt them. Elephant feeding behavior therefore benefits not only ecosystems but an entire community.

In predation, one organism hunts, kills, and eats another organism(s) for its nutrition. Predators are carnivores or omnivores, and their prey are usually omnivores and herbivores. Predators play a keystone role by regulating populations of prey animals and thereby maintaining balance within food webs. Examples of predator keystone species are wolves, lions, alligators, white sharks, and owls.

Predators furthermore keep populations of prey in check in a nonrandom manner. In other words, they do not usually attack the first prey animal they find, but rather select their prey. Predators remove old, weak, and sick animals and, as a consequence, the remaining strong and healthy population passes on its genes to offspring. Healthy prey populations then support healthier and perhaps larger predator populations. For example, years marked by very large North American deer populations have resulted in above average mountain lion populations. The converse situation may also occur in which as a prey population declines, predators regulate their numbers to avoid starvation.

Another set of relationships in biological communities comes not necessarily from feeding habits, but from other aspects of animal lifestyle. These relationships are called symbiosis, and biological communities contain three main types: mutualism, commensalism, and parasitism. In mutualism, two or more species benefit from each others’ activities. For example, the bacteria living in the gut of termites receive a safe, nutrient-rich habitat, while they provide a benefit to the termite by digesting woody food. In commensalism, one species benefits and the other is neither helped not harmed. Redwood sorrel, a small herb that lives in the shade of redwood trees, has a commensal relationship with the redwoods. Shade from the tall trees gives the sorrel its preferred habitat but the redwood tree receives no known benefit. Finally, parasitism is a relationship in which one organism benefits and the other is harmed. As an example, Phytophthora fungus lives on oak and other trees as a parasite and the fungus eventually kills the tree.

Source of Information : Green Technology Biodiversity (2010)


The Number of Species on Earth

In the species approach to conservation, biologists focus on saving individual species from extinction by studying and assessing endangered species populations and their habitats. The ecosystem approach includes studies of larger systems so that sufficient areas may be preserved to sustain healthy habitats in general.

The species approach to halting biodiversity loss depends on estimates of the number of species on Earth. The exact number will probably never be known, but the estimates used today in ecology come from counting the known species, then deriving the total number of unknown species.

The Convention on Biological Diversity has reported that 1.75 million species have been identified so far, and most scientists surmise that the actual number of all species—known and unknown—is at least 14 million. Rather than understanding the number of species on Earth, it may be more important for students of biodiversity to recognize certain hallmarks of biodiversity, as follows:

1. Species diversity increases nearer the equator.
2. Tropical rain forests cover about 7 percent of the globe’s land but hold more than 50 percent of species.
3. The loss of all species has accelerated since the year 1800.

Edward O. Wilson, curator at the Museum of Comparative Zoology at Harvard University, is one of society’s preeminent biodiversity scholars. In his classic 1988 text, Biodiversity, Wilson wrote, “No precise estimate can be made of the numbers of species being extinguished in the rain forests or in other major habitats, for the simple reason that we do not know the numbers of species originally present . . . extinction rates are usually estimated indirectly from principles of biogeography . . . the number of species of a particular group of organisms in island systems increases approximately as the fourth root of the land area. This has been found to hold true not just on real islands but also on habitat islands, such as lakes in a ‘sea’ of land, alpine meadows or mountaintops surrounded by evergreen forests, and even in clumps of trees in the midst of a grassland.” Wilson’s thoughts perhaps best sum up the reasons why counting the Earth’s species may be impossible.

Source of Information : Green Technology Biodiversity (2010)


Types of Biological Diversity

Biodiversity may be defined in five different ways. Genetic diversity, species diversity, and ecosystem diversity describe biological systems made of plants or animals, or both. Ecological diversity and functional diversity describe the Earth’s biota in large systems, such as biomes. Most people with some idea of biodiversity tend to think of species diversity, which is the number and variety of species on Earth. Biodiversity actually ranges from the molecular level within a species’ genome to a much larger scale that encompasses the entire environment.

Genetic diversity occurs at the molecular level within deoxyribonucleic acid (DNA) and in an individual’s genes. Genetic diversity causes differences between individuals within a population and, in many cases, a specific set of genes possessed by one animal enables it to survive when others in its group cannot. The idea of genetic diversity becomes clear by considering specific examples to show how this type of biodiversity gives certain individuals an advantage over others within a population.

» Cheetahs that run faster than others have a better chance at catching prey.

» Bull walruses that are bigger and stronger than other males have a better chance of breeding with females.

» The brightest colored male cardinal has the best chance of attracting females.

» Wildebeests that maneuver the best over the African savanna have a good chance of escaping lions.

» Salamanders colored in the most deceptive camouflage have an increased chance of going unnoticed by predators.

An animal’s traits come from its genotype, which is the collection of genes that make an animal look and behave as it does. Gene analysis provides information about adaptations such as speed, strength, and camouflage that enable certain individuals to thrive while others succumb. Genotypes also describe the relatedness of members in a population and between populations. Relatedness may in turn indicate declining population size, interrupted migration routes, destruction of breeding grounds, or disrupted habitat. This is because when populations become fragmented or decline in size, the diversity of the group’s members begins to decline; the individuals making up the group become more related to each other over a few generations.

Genetic diversity studies begin by taking tissue, blood, or hair samples from animals. The biologist then determines the nucleic acid sequence of the sample’s DNA to define the animal’s genotype. Any unique pattern in DNA’s gene sequence may indicate a specific trait that gives an animal favorable characteristics. Genotype can be more complicated than this simple description, however. No single gene gives a cheetah its extraordinary speed, but it may be possible to find a finite set of genes that determine a salamander’s camouflage pattern. Conservation biologists may one day be able to inject into an animal genes that will confer advantages for the animal’s survival. The pathologist John H. Wolfe at Pennsylvania’s School of Veterinary Medicine has said in a campus newsletter, “Through gene therapy, we replace a ‘broken’ gene . . . with the correct, functioning copy.” This technology may take a long time to enter conservation biology, but the fast rate of species loss demands that new technologies move quickly to save the world’s critically endangered species. Such gene manipulation will also prompt arguments from those who denounce this practice because it goes against nature and the new transgenic animal may carry potential and unknown dangers. The debate about genetically modified species continues to unfold, and no conclusions have yet come from these discussions.

Species diversity consists of two important components: richness and evenness. Species richness comprises the number of species living in a region or a community; species evenness relates to the abundance of individuals within a select species. Biologists estimate species diversity by manually counting animals in the wild within a specific region, and then illustrating the results on a map of the region. Species diversity maps almost always provide mere estimates rather than exact numbers because most animal species can be difficult to count. One technique to estimate animal numbers involves counting small groups, such as a herd or a flock, and then extrapolating those results to estimate the total population size. Though biology now has accumulated fairly accurate estimates for easy to count animals like elephants, rhinoceroses, pandas, or golden eagles, counting secretive species or ones that live in hard-to-reach habitats— snow leopards, whales, white sharks, or birds in jungle canopies—still present unique challenges.

Ecosystem diversity encompasses all of the various ecosystems known to biology. Some examples of different ecosystems are marine kelp forests, coral reefs, the African savanna, and pine forests. Ecosystem diversity also refers to the variations within ecosystems. For example, a freshwater lake is an ecosystem, but it also contains subecosystems at the lake bottom, at mid-depth, at the water’s surface, and along its banks.

Ecology is the study of ecosystems and how they relate to each other. Ecology contributes to the study of biodiversity by helping biologists gain an understanding of biomes, including the types of plants living in them, their terrain, their physical features, and their climate. The health of biomes influences the status of many of the individual species native to those biomes. For example, land that 50 years ago supported grassland contained grassland ecosystems, soil ecosystems, and possibly aquatic ecosystems in ponds and streams. After a prolonged drought due to climate change, for instance, the grassland may turn into a dry plain (desertification) and the grassland ecosystems yield to desert ecosystems. All of these events have a profound effect on the biodiversity in these places and contribute to ecological diversity.

Ecological diversity comprises the variety of forests, wetlands, grasslands, lakes, oceans, riparian areas, and other biological communities that interact with their living and nonliving environment. (A biological community is the collection of animal and plant populations living and interacting in a particular area. The populations of species that lived on the vast plains of the western United States before the 1800s are an example of a biological community.) Air and ground surveys help biologists assess ecological diversity, which in turn gives a clearer picture of ecosystem diversity.

The final type of biodiversity is functional diversity, which is the variety of biological and chemical processes (called biogeochemical cycles) that make energy and nutrients available for biota. In other words, functional diversity provides various ways for the energy-matter cycle to operate.

Source of Information : Green Technology Biodiversity (2010)



Scientists studying biodiversity must determine the number of species on the Earth and the numbers being lost to extinction. Biodiversity studies therefore rely on solid estimates of the population size of species, which is affected by species behavior, migrations, breeding cycles, and the size and distribution of habitats. All of these assessments can be rather difficult to make, especially when studying biota that live largely mysterious lifestyles in remote places.

Biodiversity measurements involve five main challenges. The first challenge comes from the difficulty of determining the number of species on Earth. Second, molecular biology is constantly revealing more about the genetic makeup of species—how they are related and why they are similar or dissimilar. Sometimes a species does not succumb to extinction, but rather it acquires genes that help it adapt to changes in the environment. Third, the characteristics that certain species require in their habitat may not be fully understood, and this makes it difficult to assess the status of a species when a habitat is altered. Fourth, not all species on Earth have been discovered, and science has no way of knowing whether or when these species go extinct or their role while they inhabit the Earth. Finally, animals oft en move around. Biologists must determine whether an animal’s population is declining or whether the species has simply migrated to a new place. A useful adage in biodiversity studies is the following: “Every animal is rare somewhere.”

Source of Information : Green Technology Biodiversity (2010)


The Biodiversity Treaty

In 1992 the United Nations convened the Earth Summit in Rio de Janeiro, Brazil, and representatives of more than 150 nations came together to discuss the preservation of species. Each nation signed the Convention on Biological Diversity, also known as the Biodiversity Treaty. This treaty called for worldwide listing of endangered and threatened species as well as cooperation among nations for their preservation, including a pay-for-use plan in which industrialized nations pay developing nations for any plants and animals they take.

Despite ambitious goals, the program fell victim to red tape and bureaucracy. Part of the problem arose from a fear that large corporations might exploit developing nations that contain most of the world’s biodiversity. Precautions against this exploitation hampered scientists’ attempt to study biodiversity in developing nations. Curator Douglas Daly of the New York Botanical Garden told the New York Times in 2002, “Something that was well intentioned and needed has been taken to an illogical extreme.” Daly and other scientists complained that it had become easier to cut down a forest than to study it.

The Biodiversity Treaty’s critics cited three central concerns. First, the pay-for-use plan created an opportunity for rich nations to exploit poorer nations, an activity called biopiracy. Second, developing countries could possibly hold their resources for ransom, and, third, the resources might disappear even faster with the treaty in place. The experience of Professor Ricardo Callejas of the University of Antioquia in Colombia highlights the difficulty of navigatinging the treaty’s rules. He explained to the New York Times the challenges of collecting a small sample of plants for his research: “If you request a permit you have to provide coordinates for all sites to be visited and have to have the approval from all the communities that live in those areas. Otherwise, go back to your home and watch on Discovery Channel the new exciting program on dinosaurs from Argentina. I am still waiting after fourteen months for a permit for collecting [black pepper species] in Choco.” Ironically, President George H. W. Bush refused to sign the treaty, claiming it was too vague. Opponents added another worry: The treaty would impede the work of pharmaceutical companies that sought new compounds from unique biota. In 1993 President Bill Clinton acknowledged those worries but agreed to sign the treaty, saying, “We cannot walk away from challenges like those presented by the biodiversity treaty. We must step up to them.” As Clinton suggested, the Biodiversity Treaty continues to play a role in conservation.

Today the treaty’s signers continue to study biodiversity-related issues such as global warming, habitat destruction, poverty, and the business aspects of environmental science. Said Callejas, “I have trouble convincing my closest friends that what I do is because of passion, curiosity, a desire to know more about a group of organisms.” Perhaps Callejas’s friends feel as many people do who think biodiversity loss has become so enormous a problem, a single treaty cannot fix it.

Source of Information : Green Technology Biodiversity (2010)