Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.

Biodiversity hotspots for conservation priorities

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Land use has generally been considered a local environmental issue, but it is becoming a force of global importance. Worldwide changes to forests, farmlands, waterways, and air are being driven by the need to provide food, fiber, water, and shelter to more than six billion people. Global croplands, pastures, plantations, and urban areas have expanded in recent decades, accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity. Such changes in land use have enabled humans to appropriate an increasing share of the planet’s resources, but they also potentially undermine the capacity of ecosystems to sustain food production, maintain freshwater and forest resources, regulate climate and air quality, and ameliorate infectious diseases. We face the challenge of managing trade-offs between immediate human needs and maintaining the capacity of the biosphere to provide goods and services in the long term.

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Global Consequences of Land Use

Human alteration of Earth is substantial and growing. Between one-third and one-half of the land surface has been transformed by human action; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning of the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined; more than half of all accessible surface fresh water is put to use by humanity; and about one-quarter of the bird species on Earth have been driven to extinction. By these and other standards, it is clear that we live on a human-dominated planet.

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Human Domination of Earth's Ecosystems

La explosión demográfica: el principal problema ecológico

Science and the Management of Natural Resources.

A central responsibility of societies should be supplying adequate nourishment to all. For roughly a third of the global human population, that goal is not met today. More ominously, that population is projected to increase some 30% by 2050. The intertwined natural and social systems, that must meet the challenge of producing and equitably distributing much more food without wrecking humanity’s life-support systems, face a daunting array of challenges and uncertainties. These have roots in the agricultural revolution that transformed our species and created civilization. Profound and multifaceted changes, revising closely-held cultural traditions and penetrating most of civilization will be required, if an unprecedented famine is to be avoided.

Food security requires a new revolution

A simple, globally aggregated, stochastic-stimulation model was constructed to examine the effects of rapid climatic change on agriculture and the human population. The model calculates population size and the production, consumption and storage of grain under different climate scenarios over a 20-year projection time. In most scenarios, either an optimistic baseline annual increase of agricultural output of 1.7% or a more pessimistic appraisal of 0.9% was used. The rate of natural increase of the human population exclusive of excess hunger-related deaths was set at 1.7% per year and climatic changes with both negative and positive impacts on agriculture were assessed. Analysis of the model suggests that the number of hunger-related deaths could double (with reference to an estimated 200 million deaths in the past two decades) if grain production keeps pace with population growth but climatic conditions are unfavourable. If the rate of increase in grain production is about half that of population growth, the number of hunger-related deaths could increase about fivefold (over past levels); the impact of climatic change is relatively small under this imbalance. Even favourable climatic changes that enhance agricultural production may not prevent a fourfold increase in deaths (over past levels) under scenarios where population growth outpaces production by about 0.8% per annum. These results may foreshadow a fundamental change where, for the first time, absolute global food deficits compound inequities in food production and distribution in causing famine. The model also highlights the effectiveness of reducing population growth rates as a strategy for minimizing the impact of global climate change and maintaining food supplies for everyone.

An exploratory model of the impact of rapid climate change on the world food situation

This paper argues that mankind is rapidly using up mineral reserves polluting the environment and destroying the biological diversity of the planet. The consequences of these actions could be catastrophic to the human race and may bring about the end of industrial civilization. The species diversity on our planet should be preserved because other species provide an array of ecosystem services without which society as we know it could not persist. Few people are aware of these ecosystem services. They include such things as maintenance of the quality of the atmosphere disposal of wastes soil maintenance food from the sea and the control of crop pests. Increased human population growth and per capita consumption lead to habitat destruction such as the paving of natural areas for mans use; the plowing of marginal land which destroys entire communities; the destruction of rain forests; and the pollution of air and water. Nature reserves must play a central role in any solution to the problem of accelerating extinctions. The author argues that the number and size of nature reserves must be increased. Efforts should be made to avoid developing new tracts of land anywhere. Instead they should be converted into reserves and everything possible should be done to make nonreserve areas more hospitable to other species. Human population will have to be controlled and the number of pollutants in the biosphere must be greatly reduced. Without these measures the earth will suffer a catastrophic loss of species.

Paul R. Ehrlich

Papers

La explosión demográfica: el principal problema ecológico

Science and the Management of Natural Resources.

Food security requires a new revolution

An exploratory model of the impact of rapid climate change on the world food situation

Human Carrying Capacity, Extinctions, and Nature Reserves