Issues in Ecology Number 2 Spring 1997 human-dominated ecosystems is undocumented in addi. As described in the previous section biodiversity tion.natural products extracted from many hundreds of is a direct source of ecosystem goods.It also supplie ies ontribute diver inputs to industrv gums and the genetic and biochemical res that under ssential oils and rings.resins nd oleo curre ultral and pha utical resins,dyes,tannins,vegetable fats and w axes,insect may allow us to adapt these vital enterprises to globa cides,and multitudes of other compounds(Myers 1983: change.Our ability to increase crop productivity in the Leung and Foster 1996).The availability of most of face of new pests.diseases.and other stresses has de these natural products is in decline due to ongoing habi- pended heavily upon the transfer to our crops of gene tat conversion from wild cror relatives that confer resistance to thes challenge Such extractions fro nbiodiversity's Generation and Maintenance of Biodiversity library account for nnual t Biologicl diversity.or biodiversity for short.re fers to the variety of life forms at all levels of organiza 1992).Biotechnology now makes possible even greate tion,from the molecular to the land- use of this natural storehouse of ge. scape level.Biodiversity is generated netic diversity via the transfer to crops and maintained in natural ecosystems of genes from any kind of organisn where organisms counter a wide not simply crop relative and it variety of livi ing cond tions pro 6 play a majd role in fu events that shape their evolution in ture yield increase By the e turn unique ways.Out of convenience or the.farm-evelsae f th necessity.biodiversity is usually quan products of agricultural biotechnol tified in terms of numbers of species ogy,iust now entering the market and this perspective has greatly influ- ce,are expected to reach at least enced atio It is i rtant to ren however, 1991 cited (World Bank tal.1996 In addition to sustaining the produc to humanity are delivered througl tion of conventional crops,the populations of species residing in liv biodiversity in natural ecosystems may ing communities within specific physi include many potential new foods cal settings-in other words.through Human beings have utilized around comple syste 7 000 plant sn ies for food ov systems (Daily and) story and ar .70.000 beings to realize most of the nts are aesthetic,spiritual,and economic ben Wilson 1989).Only about 150 food efits of biodiversity,natural ecosys Figure 4-Harpoon-whaling in olants have ever been cultivated on a tems must therefore be accessible.the The o re a key sourc large scale,however.Currently.82 continued existence of coniferous tree of animal protein for the human popu plant species contribute 90 percen species somewhere in the world would lation. of national per-capita supplies of food not help the inhab itants of a tov ants ott-Allen undated by ng be ause of the clearing of a pin a much smalle er numbe forest upstream.Generally,the flow of ecosystem goods of these supply the bulk of the calories humans consume and services in a region is determined by the type,spa- Many other species,however,appear more nutritious or tial layout.extent.and proximity of the ecosystems sup better suited to the growing conditions that prevail in plying them.Because of this,the preservation of only important regions than the standard crops that dom one minimum viable population of each non-human spe nate world food supply today. Because of increasin and the world' eprtectedra wot iation ofirigate nds and the otential for d security it.Indeed,such a strategy.taken to extreme,would leac may come to depend on drought-and salt-tolerant vari to collapse of the biosphere,along with its life support eties that now play comparatively minor roles in agricul services. ture
As described in the previous section, biodiversity is a direct source of ecosystem goods. It also supplies the genetic and biochemical resources that underpin our current agricultural and pharmaceutical enterprises and may allow us to adapt these vital enterprises to global change. Our ability to increase crop productivity in the face of new pests, diseases, and other stresses has depended heavily upon the transfer to our crops of genes from wild crop relatives that confer resistance to these challenges. Such extractions from biodiversitys genetic library account for annual increases in crop productivity of about 1 percent, currently valued at $1 billion (NRC 1992). Biotechnology now makes possible even greater use of this natural storehouse of genetic diversity via the transfer to crops of genes from any kind of organism not simply crop relativesand it promises to play a major role in future yield increases. By the turn of the century, farm-level sales of the products of agricultural biotechnology, just now entering the marketplace, are expected to reach at least $10 billion per year (World Bank 1991, cited in Reid et al. 1996). In addition to sustaining the production of conventional crops, the biodiversity in natural ecosystems may include many potential new foods. Human beings have utilized around 7,000 plant species for food over the course of history and another 70,000 plants are known to have edible parts (Wilson 1989). Only about 150 food plants have ever been cultivated on a large scale, however. Currently, 82 plant species contribute 90 percent of national per-capita supplies of food plants (Prescott-Allen and Prescott-Allen 1990), although a much smaller number of these supply the bulk of the calories humans consume. Many other species, however, appear more nutritious or better suited to the growing conditions that prevail in important regions than the standard crops that dominate world food supply today. Because of increasing salinization of irrigated croplands and the potential for rapid climate change, for instance, future food security may come to depend on drought- and salt-tolerant varieties that now play comparatively minor roles in agriculture. 5 Issues in Ecology Number 2 Spring 1997 Photo by Taylor Ricketts Figure 4-Harpoon-whaling in Flores, Indonesia. The oceans are a key source of animal protein for the human population. human-dominated ecosystems is undocumented. In addition, natural products extracted from many hundreds of species contribute diverse inputs to industry: gums and exudates, essential oils and flavorings, resins and oleoresins, dyes, tannins, vegetable fats and waxes, insecticides, and multitudes of other compounds (Myers 1983; Leung and Foster 1996). The availability of most of these natural products is in decline due to ongoing habitat conversion. Generation and Maintenance of Biodiversity Biological diversity, or biodiversity for short, refers to the variety of life forms at all levels of organization, from the molecular to the landscape level. Biodiversity is generated and maintained in natural ecosystems, where organisms encounter a wide variety of living conditions and chance events that shape their evolution in unique ways. Out of convenience or necessity, biodiversity is usually quantified in terms of numbers of species, and this perspective has greatly influenced conservation goals. It is important to remember, however, that the benefits that biodiversity supplies to humanity are delivered through populations of species residing in living communities within specific physical settings in other words, through complex ecological systems, or ecosystems (Daily and Ehrlich 1995). For human beings to realize most of the aesthetic, spiritual, and economic benefits of biodiversity, natural ecosystems must therefore be accessible. The continued existence of coniferous tree species somewhere in the world would not help the inhabitants of a town inundated by flooding because of the clearing of a pine forest upstream. Generally, the flow of ecosystem goods and services in a region is determined by the type, spatial layout, extent, and proximity of the ecosystems supplying them. Because of this, the preservation of only one minimum viable population of each non-human species on Earth in zoos, botanical gardens, and the worlds legally protected areas would not sustain life as we know it. Indeed, such a strategy, taken to extreme, would lead to collapse of the biosphere, along with its life support services.
Issues in Ecology Number 2 Spring 1997 Tuming to medicinal res urces 20.000 years ago,for example,much of Europe an showed that top 150 th Am red by mi -thick ice the United States are on natura sources While the imate has been la vel stable since 74%on plants.I8%on fungi.5%on bacteria,and 3% the invention of agriculture around 10,000 years ago on one vertebrate (snake)species. Nine of the top ten periodic shifts in climate have affected human activities drugs in this list are based on natural plant products and settlement patterns.Even relatively recently,from (Grifo and Rosenthal,in press.as cited in Dobson 1995) 1550-1850.Europe was significantly cooler during a The commercial value of pharmaceuticals in the devel period known as the Little lceAge.Many of thesechar n per year( nate are thought to be aused by altera mately Earth's orbita the energy outpu t of the human population relies on traditional medical systems, sun,or even by events on the Earth itself sudden per and about 85%of traditional medicine involves the use turbations such as violent volcanic eruptions and aster of plant extracts(Farnsworth et al.1985). oid impacts or more gradual tectonic events such as the Saving only a single popula tion of each species could have an othe cost. Different pop gh all these the same species may pro change e diffe life year ent types or quantities of defensive (Schneider and Londer 1984). An chemicals that have potential use as life itself has played a role in this buff- pharmaceuticals or pesticides ering. (McCormick et al.1993):and they Climate.of course.plays a may exhibit different tolerances maior role in the evolution and distri onmental stresses such the pla et.Yet m salinity. scienti d agree hat life i se is a principal factor in the regulati therapeutic antibiotic took a full 15 of global climate.helping to offset the years after Alexander Fleming's fa- effects of episodic climate oscillations mous discovery of it in common bread by responding in ways that alter the mold.In part.this was because greenhouse gas concentrations in the ntistshad great ere for instance nat extracting. the sul systems may have helped to stabi stance in needed quantities One key climate and prevent overheating of the to obtaining such quantities was the Figure 5-Trapping and releasing butterflies Earth by removing more of the green discovery.after a worldwide search in a mixed-agriculture landscape in Costa house gas carbon dioxide from the of a ponulation of Fleming's mold that Rica.Monitorine the impact of humar atmosphere as the sun grew brighter produced more penicillin than the activities on biodiversity and ecosysten over millions of vears (Alexander et Similarly. services is needed worldwide:butterflie ,1997).ife also evert a de ary in thei may be useful indi cators for monitoring. or positive feedback to resist pests and diseas traits im reinforces climate change,particularly portant in agriculture.Many thousands of varieties of during transitions between interglacial periods and ice rice from different locations were screened to find one ages.One example:When climatic cooling leads to drops with resistance to grassy stunt virus,a disease that posed in sea level.continental shelves are exposed to wind and a serious threat to the world's rice crop(Myers 1983). rain.causing greater nutrient runoff to the oceans.thes Des pite these the vth of r anktor es of crops remain unpro form c ium carb nate shells tected and heavily threatened populations would remove more carbon dioxide e from the oceans and the atmosphere.a mechanism that should Climate and life further cool the planet.living things may also enhance Earth's climate has fluctuated tremendously since warming trends through such activities as speeding up humanity came into being.At the peak of the last ice microbial decomposition of dead organic matter.thus
6 Issues in Ecology Number 2 Spring 1997 Figure 5-Trapping and releasing butterflies in a mixed-agriculture landscape in Costa Rica. Monitoring the impact of human activities on biodiversity and ecosystem services is needed worldwide; butterflies may be useful indicators for monitoring. Photo by Paul R. Ehrlich Turning to medicinal resources, a recent survey showed that of the top 150 prescription drugs used in the United States, 118 are based on natural sources: 74% on plants, 18% on fungi, 5% on bacteria, and 3% on one vertebrate (snake) species. Nine of the top ten drugs in this list are based on natural plant products (Grifo and Rosenthal, in press, as cited in Dobson 1995). The commercial value of pharmaceuticals in the developed nations exceeds $40 billion per year (Principe 1989). Looking at the global picture, approximately 80% of the human population relies on traditional medical systems, and about 85% of traditional medicine involves the use of plant extracts (Farnsworth et al. 1985). Saving only a single population of each species could have another cost. Different populations of the same species may produce different types or quantities of defensive chemicals that have potential use as pharmaceuticals or pesticides (McCormick et al. 1993); and they may exhibit different tolerances to environmental stresses such as drought or soil salinity. For example, the development of penicillin as a therapeutic antibiotic took a full 15 years after Alexander Flemings famous discovery of it in common bread mold. In part, this was because scientists had great difficulty producing, extracting, and purifying the substance in needed quantities. One key to obtaining such quantities was the discovery, after a worldwide search, of a population of Flemings mold that produced more penicillin than the original (Dowling 1977). Similarly, plant populations vary in their ability to resist pests and disease, traits important in agriculture. Many thousands of varieties of rice from different locations were screened to find one with resistance to grassy stunt virus, a disease that posed a serious threat to the worlds rice crop (Myers 1983). Despite numerous examples like these, many of the localities that harbor wild relatives of crops remain unprotected and heavily threatened. Climate and Life Earths climate has fluctuated tremendously since humanity came into being. At the peak of the last ice age 20,000 years ago, for example, much of Europe and North America were covered by mile-thick ice sheets. While the global climate has been relatively stable since the invention of agriculture around 10,000 years ago, periodic shifts in climate have affected human activities and settlement patterns. Even relatively recently, from 1550-1850, Europe was significantly cooler during a period known as the Little Ice Age. Many of these changes in climate are thought to be caused by alterations in Earths orbital rotation or in the energy output of the sun, or even by events on the Earth itselfsudden perturbations such as violent volcanic eruptions and asteroid impacts or more gradual tectonic events such as the uplift of the Himalayas. Remarkably, climate has been buffered enough through all these changes to sustain life for at least 3.5 billion years (Schneider and Londer 1984). And life itself has played a role in this buffering. Climate, of course, plays a major role in the evolution and distribution of life over the planet. Yet most scientists would agree that life itself is a principal factor in the regulation of global climate, helping to offset the effects of episodic climate oscillations by responding in ways that alter the greenhouse gas concentrations in the atmosphere. For instance, natural ecosystems may have helped to stabilize climate and prevent overheating of the Earth by removing more of the greenhouse gas carbon dioxide from the atmosphere as the sun grew brighter over millions of years (Alexander et al. 1997). Life may also exert a destabilizing or positive feedback that reinforces climate change, particularly during transitions between interglacial periods and ice ages. One example: When climatic cooling leads to drops in sea level, continental shelves are exposed to wind and rain, causing greater nutrient runoff to the oceans. These nutrients may fertilize the growth of phytoplankton, many of which form calcium carbonate shells. Increasing their populations would remove more carbon dioxide from the oceans and the atmosphere, a mechanism that should further cool the planet. Living things may also enhance warming trends through such activities as speeding up microbial decomposition of dead organic matter, thus