Biological diversity consists of three components:

• Landscape and community diversity.
  A natural landscape is a mosaic of different patches, recognizable by physical characteristics and vegetation. A typical Nevada landscape may consist of sagebrush flats, pinyon juniper woodlands, and riparian zones. Each of these vegetation types, or communities, consists of interdependent plants, animals, and microorganisms associated with particular kinds of soil, climate, and disturbance patterns. Various types of aquatic communities also are found in the state.
• Species diversity.
  Nevada has about 110 species of mammals, 450 species of birds, 55 species of amphibians and reptiles, 65 species of fish, 3,000 species of vascular plants, and an unknown number of invertebrates and microbial organisms. Some of these use several components if landscape diversity, while others live in very specialized habitats.
• Genetic diversity.
  All individuals in most species are genetically different from each other (which is easy to see in people and puppies). These genetic differences enable species to survive and adapt in response to changing environmental conditions. With limited genetic diversity change becomes more difficult or impossible.

Thus, communities in landscapes, species, and genes are the components of biological diversity. Each of these components is maintained in ecosystems (a geographic area functioning as an ecological unit) by a variety of interacting ecological processes.

Why Is Biodiversity Important?

• The Global Life Support System.
  Life on earth is dependent on five basic processes:

1. Primary productivity.
The conversion of carbon dioxide and water into living material via the process of photosynthesis in green plants, is the basis for every other life process-the growth of plants, the production of crops, and the transfer of this energy along food chains to animals, including humans.

2. The building and maintenance of soil fertility.
The decomposition of organic matter and the recycling of key nutrients such as nitrogen, phosphorus, and sulfur in the soil is driven by animals, microbes, and fungi. Plants protect the soil from excess erosion.

3. The regulation of the hydrologic cycle.
Fresh water is recirculated among living material, the soil, the atmosphere, and the surface and ground water reserves. This is both a biological and physical process. To grow, plants must move water from the soil into the atmosphere, and both plants and animals (such as earthworms and termites) slow runoff and increase water filtration by increasing soil porosity.

4. The control and amelioration of climate.
The participation of plants in the hydrologic cycle stimulates local and regional rainfall, and the vegetation creates microclimates in which other species can live.

5. The maintenance of the composition and quality of the atmosphere.
All atmospheric oxygen is of biological origin, and biological processes regulate the abundance of many atmospheric gases such as methane and carbon dioxide.

These five biological, chemical, and physical processes comprise the global life-support system on which our economic, social, cultural, and political systems depend. All of these processes involve biodiversity. Clearly, conserving biodiversity is critical to the human enterprise.

• Ecological Services
In addition to maintaining the global life support system, biodiversity provides humans with numerous services which are largely unappreciated by the general public. These services provide direct economic benefits and are very expensive-or impossible-to replace.

1. The regulation of fresh water supplies and the control of flooding.
Wetlands and floodplains act as giant sponges to soak up moisture during wet periods and release it slowly during dry periods. The Mississippi floods of 1993 caused over $19 billion in damage; however, a recent article in American Scientist showed that if only five percent of the bottomland (strategically placed) had been left as natural wetlands, most of this damage could have been prevented.

2. The control of pests and diseases.
Three examples:

• Bats are a primary predators of beetles, moths, leafhoppers, and other insects that cost farmers and foresters billions of dollars every year. The 20 million free-tailed bats that live in Bracken Cave in Central Texas eat 250 tons of insects during a single midsummer night. The economic impacts of this have not been calculated but are not hard to imagine.
• A single pair of long-eared owls will eat between 850-1500 rodents per year. In Sierra Nevada, most of these are deer mice, the primary reservoir of hanta virus. The additional risks to human health would be substantial if these owls weren't at work.
• A recent experiment showed that the growth rates of trees from which insectivorous birds had been excluded were 25% lower than the growth rates of trees that the birds could access. This is because the birds consume herbivorous insects, mostly caterpillars, that eat much of the trees' primary productivity.

3. The pollination and dispersal of crops and useful wild plants and fungi.
Three examples:
• More than 450 commercial products, including fibers, dyes, fuels, medicines, and timber come from plants which are pollinated by bats. Without the pollination services, many of these products (including tequila) would simply not be produced.
• Many crop plants in the squash family (e.g. cantelopes, pumpkins) are pollinated by certain species of bees that live in uncultivated land adjacent to agricultural areas. If these bees are not present in the natural ecosystems surrounding the crops, the plants have to be pollinated by hand since domestic honeybees are not effective. Because of inappropriate pesticide spraying and plowing too close to fence rows, squash bees are becoming scarce in many agricultural areas. As a result, some regions in the US suffered shortages of pumpkins and squashes this year.
• The dispersal of several important conifers such as whitebark pine, depends on the seed caching behavior of a few bird species, mainly jays and Clark's nutcrackers. Without the activities of these birds, these trees would be unable to recolonize after fires or other disturbances.

4. The provision of fish, timber, and other products that are important for commercial and recreational harvest.
This ecosystem service is well known and obviously has important economic implications. As one example, the recreational fishing industry in the US is worth $24 billion per year. Despite considerable progress under the Clean Water Act, water quality is still declining in some areas, and this economic benefit is likely to wane. Public health warnings to avoid or limit fish consumption were issued in 46 states for thousands of water bodies in 1994, a 20% increase since 1993. Sixty percent of these were related to mercury contamination.

5. The provision of wildlife and other amenities for non-consumptive uses.
This has important benefits as well. For an example, a recent study of the economic impact of bird watching was conducted at the Forsythe National Wildlife Refuge in New Jersey. Of the 130,000 annual visitors, 75% were birders; the rest either fished or hunted. The birders spent $27 million in one year (1993-1994) on their trips to and from the refuge, and the economic impact on the local economy was calculated at $4 million, spent on lodging, meals, gas, and other expenses.

6. The storehousing of useful products.
Thousands of plants, animals, and microbes found in natural ecosystems provide, or have the potential to provide, medicines, foods, disease resistance in crop plants, raw materials for genetic engineering, and other economical valuable products. For example, Francesca Grifo of the American Museum of Natural History in New York showed that 79% of the top 150 prescription drugs sold worldwide are based directly on compounds synthesized by wild species. Seventy-four percent of these are from plants, 18% are from fungi, 5% from bacteria, and 3% from invertebrates.

Furthermore, nine of the top prescription drugs in the US are based on natural plant products. Unfortunately, we are currently very ignorant of the extent of this potential. A mere 1,100 of the world's 365,000 known species of plants have been examined for their medicinal properties.

New drugs are urgently needed for several reasons. First, there is an increasingly widespread resistance to many antibiotics currently in use, resulting in a resurgence of older diseases such as tuberculosis. Second, new diseases (hanta virus, ebola virus, HIV, etc.) are emerging at increasing rates. Third, global climate change will cause changes in the distributions of disease organisms and their vectors, increasing their exposure to human populations.

Finally, genetic diversity stored within species is not only important to species themselves, but also to humans directly. Two examples:

• The Pyramid Lake strains of Lahontan cutthroat trout had the genetic ability to grow to 20-25 pounds on average and to more than 40 pounds occasionally. This genetic ability was lost when the strains went extinct, although other strains of Lahontan cutthroat trout still survive.
• The Alvord trout was a strain of Lahontan cutthroat trout which grew very large in small streams and was able to survive in hot, low oxygen conditions that kill other trout. These two trout strains would be extremely valuable to the sportfishing industry now.

• Moral And Ethical Reasons
Species are produced either by hundreds of thousands of years of evolution or by divine creation, depending on one's philosophical perspective. For these reasons alone, few people would argue that it is morally right for human beings to eliminate other species. This may be the most potent argument of all for preserving biodiversity.

What Can Be Done To Promote Biodiversity Conservation?
Everyone should understand thoroughly the concept of biodiversity, its importance to the human enterprise, and the threats facing it. Once comfortable with the concept, people need to educate others about opportunities to enhance their lives and the lives of others by the improved management of biological resources. In particular, the false dichotomy of "environment vs. jobs" must be refuted.

In Nevada, some of the greatest threats to native biodiversity are highly competitive exotic plants and animals, fire suppression in certain natural ecosystems, and water diversions for agricultural, industrial, and urban use. These complex problems illustrate the need for people with many different skills and perspectives to work together and create workable, mutual-interest solutions to sustain both the economy and its underlying ecological systems.

Summary
Biodiversity runs the global life support system on which the entire human enterprise depends. Biodiversity also provides humanity with numerous immediately tangible benefits that are little appreciated, many of which have direct economic returns.

People impact biological diversity in many ways. The current wave of species extinction results almost entirely from human activities. Although progress is being made, the way in which most of our biological resources such as forests, fisheries, or rangelands are being managed is not sustainable. This will have to change if future generations are to have the same opportunities enjoyed by the present generation. Those who claim that there is a choice between the needs of the people and the environment are simply wrong. Human well-being depends on a fully functional environment, and a fully functional environment depends on biological diversity.