Conservation of Biodiversity

Currently the planet is inhabited by several million species in about 100 different phyla (Dirzo & Raven 2003). About 1.8 million have been described by scientists (Hilton-Taylor et al. 2008), but conservative estimates suggest that there are 5–15 million species alive today (May, 2000), since many groups of organisms remain poorly studied. Over 15,000 new species are described each year (Dirzo & Raven 2003), and new species are evolving during our lifetimes. However, modern extinction rates are high, at 100 to 1000 times greater than background extinction rates calculated over the eras (Hambler 2004). Although new species appear, existing species go extinct at a rate 1000 times that of species formation (Wilson 2003). Many biologists agree that we are in the midst of a mass extinction, a time when 75% or more of species are lost over a short geological time scale (Raup 1994). The last great mass extinction was 65 million years ago, at the end of the Cretaceous, when the dinosaurs went extinct. The International Union for the Conservation of Nature estimates that 22% of known mammals, 32% of amphibians, 14% of birds, and 32% of gymnosperms (all well-studied groups) are threatened with extinction (Hilton-Taylor et al. 2008). Species that were abundant within the last 200 years have gone extinct. For example, passenger pigeons, which numbered three to five billion in the mid 1800s (Ellsworth & McComb 2003), are now extinct.

Why should we be concerned about this loss of biodiversity? The answer lies in the fact that, for the first time in Earth’s history, a single species, Homo sapiens, could cause a mass extinction, precipitating its own demise. The primary cause of today’s loss of biodiversity is habitat alteration caused by human activities.

Let’s think about the meaning of biodiversity. Most people understand that biodiversity includes the great heterogeneous assemblage of living organisms. This aspect of biodiversity is also known as "species diversity." Biodiversity includes two other components as well- genetic diversity and ecosystem diversity.

The 1.8 million species described by science are incredibly diverse. They range from tiny, single-celled microbes like Nanoarchaeum equitans, 400 nm in diameter living as parasites on other microbes in thermal vents at temperatures of 70–98°C (Huber et al. 2002), to giant organisms like Sequoias, blue whales, the "humungous fungus," and "Pando" (Figure 1). "Pando" is the name given to a clonal stand of aspen trees, all genetically identical and attached to each other by the roots (Grant et al. 1992). The stand covers 106 acres and weighs 13 million pounds. The "humungous fungus," a giant individual of the species Armillaria oysterae is found in the state of Oregon, and covers 1,500 acres (USDA Forest Service 2003).

While people are generally most familiar with multicellular organisms such as plants and animals, these organisms form only small branches on the tree of life. The greatest metabolic diversity is found among the prokaryotic organisms of the Eubacteria and Archaea. Although some of these microbes use oxygen for respiration, or photosynthesize like plants, others have the extraordinary ability to derive energy from inorganic chemicals such as hydrogen sulfide or ammonia, and they use carbon dioxide as their only source of carbon for producing organic molecules. Organisms that we consider extremophiles can survive in saturated salt concentrations (36% compared to approximately 3% for seawater), or in superheated water in deep-sea vents and geysers.

Because people have ventured to all parts of the globe, one might expect that the new species being discovered each year would be microscopic organisms that can only be distinguished at the metabolic level. While it is true that most new species identified are insects, microbes and fungi, we are still discovering new vertebrates (Figure 2), even sizable new vertebrates such as a new species of baleen whale and a clouded leopard. Since 2000, 53 new species of primates have been described (IUCN 2008) including a new species of Brazilian monkey, Mura’s saddleback tamarin.

Genes are responsible for the traits exhibited by organisms and, as populations of species decrease in size or go extinct, unique genetic variants are lost. Since genes reside within species, why should we consider genetic diversity as a separate category? Because they hold "genetic potential." For example, many of the crops that we grow for food are grown in monocultures of genetically homogeneous individuals. Because all individuals are the same, a disease, insect pest, or environmental change that can kill one individual can extirpate an entire crop. Most of our high-yield varieties show significant reductions in yield within about 5 years, as pests overcome the crops’ natural defenses. Plant breeders look to wild plant relatives and to locally grown landraces to find new genetic varieties. They can then introduce these genes into crops to renew their vigor. However, according to the UN Food and Agriculture Organization, 96% of the 7,098 US apple varieties cultivated prior to 1904, 95% of the US cabbage varieties, and 81% of tomato varieties, are extinct, and the genes that made these varieties unique are gone.

Genetic variation allows species to evolve in response to diseases, predators, parasites, pollution, and climate change. The Red Queen Hypothesis, named for Lewis Carroll’s character who runs continually in order to stay in the same place, states that organisms must continually evolve, or succumb to their predators and parasites that will continue to evolve.

In addition to traditional breeding, advances in genetic engineering have allowed scientists to introduce beneficial genes from one species to another. For example, diabetics used to depend on insulin from human cadavers, or from cows or pigs. Human insulin was expensive, and non-human insulin could cause allergic reactions. Now we can isolate the gene that codes for human insulin, insert it into bacterial cells, and let the bacteria produce large quantities of human insulin. Other notable feats in genetic engineering include the introduction of genes that enhance the nutritive value of food, create crop resistance to insect pests, induce sheep to produce a protein for treating cystic fibrosis disease, and alter bacteria so that they can clean up toxic mine wastes through their metabolic activities. Many other genetic manipulations are currently in development.

Ecosystems include all the species, plus all the abiotic factors characteristic of a region. For example, a desert ecosystem has soil, temperature, rainfall patterns, and solar radiation that affect not only what species occur there, but the morphology, behavior, and the interactions among those species (Figure 3). When ecosystems are intact, biological processes are preserved. These processes include nutrient and water cycling, harvesting light through photosynthesis, energy flow through the food web, and patterns of plant succession over time. A conservation focus on preserving ecosystems not only saves large numbers of species (including non-charismatic species that do not receive public support) but also preserves the support systems that maintain life

From a selfish point of view, humans should be concerned about saving biodiversity because of the benefits it provides us–biological resources and ecosystem services. However, nature provides social and spiritual benefits as well.