William H. Schlesinger

Bio: William H. Schlesinger is an academic researcher from Institute of Ecosystem Studies. The author has contributed to research in topics: Soil water & Carbon cycle. The author has an hindex of 95, co-authored 273 publications receiving 54711 citations. Previous affiliations of William H. Schlesinger include University of California, Santa Barbara & Oklahoma State University–Stillwater.

Human alteration of the global nitrogen cycle: sources and consequences

Abstract: Nitrogen is a key element controlling the species composition, diversity, dynamics, and functioning of many terrestrial, freshwater, and marine ecosystems. Many of the original plant species living in these ecosystems are adapted to, and function optimally in, soils and solutions with low levels of available nitrogen. The growth and dynamics of herbivore populations, and ultimately those of their predators, also are affected by N. Agriculture, combustion of fossil fuels, and other human activities have altered the global cycle of N substantially, generally increasing both the availability and the mobility of N over large regions of Earth. The mobility of N means that while most deliberate applications of N occur locally, their influence spreads regionally and even globally. Moreover, many of the mobile forms of N themselves have environmental consequences. Although most nitrogen inputs serve human needs such as agricultural production, their environmental conse- quences are serious and long term. Based on our review of available scientific evidence, we are certain that human alterations of the nitrogen cycle have: 1) approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing; 2) increased concentrations of the potent greenhouse gas N 2O globally, and increased concentrations of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth; 3) caused losses of soil nutrients, such as calcium and potassium, that are essential for the long-term maintenance of soil fertility; 4) contributed substantially to the acidification of soils, streams, and lakes in several regions; and 5) greatly increased the transfer of nitrogen through rivers to estuaries and coastal oceans. In addition, based on our review of available scientific evidence we are confident that human alterations of the nitrogen cycle have: 6) increased the quantity of organic carbon stored within terrestrial ecosystems; 7) accelerated losses of biological diversity, especially losses of plants adapted to efficient use of nitrogen, and losses of the animals and microorganisms that depend on them; and 8) caused changes in the composition and functioning of estuarine and nearshore ecosystems, and contributed to long-term declines in coastal marine fisheries.

Biogeochemistry : An Analysis of Global Change

Abstract: Part 1 Processes and reactions: origins the atmosphere the lithosphere the terrestrial biosphere biogeochemical cycling on land biogeochemistry in freshwater wetlands and lakes rivers and estuaries the sea. Part 2 Global cycles: the global water cycle the global carbon cycle the global cycle of nitrogen and phosphorous the global sulfur cycle a perspective.

Forecasting agriculturally driven global environmental change

Abstract: During the next 50 years, which is likely to be the final period of rapid agricultural expansion, demand for food by a wealthier and 50% larger global population will be a major driver of global environmental change. Should past dependences of the global environmental impacts of agriculture on human population and consumption continue, 10(9) hectares of natural ecosystems would be converted to agriculture by 2050. This would be accompanied by 2.4- to 2.7-fold increases in nitrogen- and phosphorus-driven eutrophication of terrestrial, freshwater, and near-shore marine ecosystems, and comparable increases in pesticide use. This eutrophication and habitat destruction would cause unprecedented ecosystem simplification, loss of ecosystem services, and species extinctions. Significant scientific advances and regulatory, technological, and policy changes are needed to control the environmental impacts of agricultural expansion.

The global carbon dioxide flux in soil respiration and its relationship to vegetation and climate

Abstract: We review measured rates of soil respiration from terrestrial and wetland ecosystems to define the annual global CO 2 flux from soils, to identify uncertainties in the global flux estimate, and to investigate the influences of temperature, precipitation, and vegetation on soil respiration rates. The annual global CO 2 flux from soils is estimated to average (± S.D.) 68 ± 4 PgC/ yr, based on extrapolations from biome land areas. Relatively few measurements of soil respiration exist from arid, semi-arid, and tropical regions; these regions should be priorities for additional research. On a global scale, soil respiration rates are positively correlated with mean annual air temperatures and mean annual precipitation. There is a close correlation between mean annual net primary productivity (NPP) of different vegetation biomes and their mean annual soil respiration rates, with soil respiration averaging 24% higher than mean annual NPP. This difference represents a minimum estimate of the contribution of root respiration to the total soil CO 2 efflux. Estimates of soil C turnover rates range from 500 years in tundra and peaty wetlands to 10 years in tropical savannas. We also evaluate the potential impacts of human activities on soil respiration rates, with particular focus on land use changes, soil fertilization, irrigation and drainage, and climate changes. The impacts of human activities on soil respiration rates are poorly documented, and vary among sites. Of particular importance are potential changes in temperatures and precipitation. Based on a review of in situ measurements, the Q 10 value for total soil respiration has a median value of 2.4. Increased soil respiration with global warming is likely to provide a positive feedback to the greenhouse effect. DOI: 10.1034/j.1600-0889.1992.t01-1-00001.x

Biological Feedbacks in Global Desertification

Abstract: Studies of ecosystem processes on the Jornada Experimental Range in southern New Mexico suggest that longterm grazing of semiarid grasslands leads to an increase in the spatial and temporal heterogeneity of water, nitrogen, and other soil resources. Heterogeneity of soil resources promotes invasion by desert shrubs, which leads to a further localization of soil resources under shrub canopies. In the barren area between shrubs, soil fertility is lost by erosion and gaseous emissions. This positive feedback leads to the desertification of formerly productive land in southern New Mexico and in other regions, such as the Sahel. Future desertification is likely to be exacerbated by global climate warming and to cause significant changes in global biogeochemical cycles.

The Theory of Island Biogeography

Abstract: 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

Global Consequences of Land Use

Abstract: 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.

Food Security: The Challenge of Feeding 9 Billion People

Abstract: Continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years. Growing competition for land, water, and energy, in addition to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. But the world can produce more food and can ensure that it is used more efficiently and equitably. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security, different components of which are explored here.

Human Domination of Earth's Ecosystems

Abstract: 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.