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.thus6 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 devel￾oped 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 popula￾tion of each species could have an￾other cost. Different populations of the same species may produce differ￾ent 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 Fleming’s fa￾mous discovery of it in common bread mold. In part, this was because sci￾entists had great difficulty producing, extracting, and purifying the sub￾stance in needed quantities. One key to obtaining such quantities was the discovery, after a worldwide search, of a population of Fleming’s mold that produced more penicillin than the original (Dowling 1977). Similarly, plant populations vary in their ability to resist pests and disease, traits im￾portant 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 world’s rice crop (Myers 1983). Despite numerous examples like these, many of the lo￾calities that harbor wild relatives of crops remain unpro￾tected and heavily threatened. Climate and Life Earth’s 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 Earth’s orbital rotation or in the energy output of the sun, or even by events on the Earth itselfsudden per￾turbations such as violent volcanic eruptions and aster￾oid 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 buff￾ering. Climate, of course, plays a major role in the evolution and distri￾bution 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 eco￾systems may have helped to stabilize climate and prevent overheating of the Earth by removing more of the green￾house gas carbon dioxide from the atmosphere as the sun grew brighter over millions of years (Alexander et al. 1997). Life may also exert a de￾stabilizing 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