MINNEAPOLIS / ST. PAUL--If current trends in the growth of global population and wealth continue, the planet will lose a billion hectares of natural ecosystems--an area the size of the United States--to agriculture by the year 2050, according to projections by an international team of scientists led by University of Minnesota ecologist David Tilman. The work, to be published in the April 13 issue of Science, examines nonclimatic global environmental impacts of agricultural expansion, such as increased nitrogen, phosphorus and pesticide deposition and demand for irrigation water, which will accompany rises in population and per capita wealth.

"Environmental impacts of agriculture will be as great as or greater than the impacts of climate change," said Tilman, who holds the McKnight President Endowed Chair in Ecology at the university. While acknowledging that the forecasts are not predictions and that shifts in technology, environmental regulations, human behavior and other factors could throw off the projections, Tilman said he and his colleagues aimed to keep their estimates conservative. Using four statistical techniques, they made four forecasts of each variable. Only the mean value of each forecast is reported here.

Basing their forecasts on agricultural uses of nitrogen, phosphorus and irrigation brought about by the Green Revolution, the authors forecast that if past trends continue, global nitrogen fertilization will be 1.6 times present amounts by 2020 and 2.7 times present amounts by 2050. For phosphorus, the numbers are 1.4 times (2020) and 2.4 times (2050). Irrigated land would increase to 1.3 times present area (2020) and 1.9 times (2050). Nitrogen and phosphorus leakage from farms is already a problem in many areas, partly because 70 percent of harvested crops are fed to livestock, but little animal waste is treated for nitrogen or phosphorus removal. Irrigation not only consumes fresh water, but causes salt and nutrient loading to downstream bodies of water. Phosphorus leads to blooms of algae and resultant degradation of freshwater lakes and streams. Projected pesticide use has risen for the last 40 years and would be 1.7 times present use (2020) and 2.7 times present use (2050), according to the scientists' calculations.

Most of the projected billion-hectare increase in cropland and pastureland is expected to occur in developing countries, predominantly Latin America and sub-Saharan Africa. The conversion to agriculture would likely come at the expense of approximately a third of remaining tropical and temperate forests, savannas and grasslands. Should that happen, these ecosystems would no longer be able to store carbon, produce oxygen and water (through photosynthesis and transpiration, respectively) or perform other "ecosystem services" on nearly the scale they do now. Losses of these ecosystems to agriculture would be added to losses expected from urban and suburban development, roads and other human expansions, and species extinction would be an inevitable consequence of habitat destruction. Driving the agricultural expansion is not only population growth, but a growth in wealth, which is associated with a higher demand for meat. The authors foresee a 50 percent growth in population by 2050, accompanied by a doubling in demand for food.

A bright spot is that these projections are based on current practices and trends, and those could change. Comprehensive land-use planning could soften some of the impacts. For example, planting of cover crops on fallow land and strips of vegetation to intercept nutrients and pesticide runoff between farmland and drainage areas could mitigate some impacts. Also, advances in and widespread use of precision agriculture techniques could reduce amounts of fertilizer and pesticide applied to fields. Better ways to contain pests and to treat livestock waste are also needed. But the scale of change will be so great, the scientists said, that major international efforts will be required to supply the technologies and policies necessary for ecologically sustainable agriculture.

"Agriculture is the last major unregulated source of environmental pollution, and it will increase two- to three-fold in the next 50 years," said Tilman. "If this expansion is done in the way it's been done for the last 50 years, we'll have irreversible environmental damage. But if we change, we can turn the corner." Working with Tilman were colleagues from the University of California, Berkeley; Princeton University; the Woods Hole Marine Biological Laboratory; the University of Alberta; Duke University; the University of Tennessee, Knoxville; and the University of Minnesota. The work was funded by the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara, which is supported by the National Science Foundation.
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"We already know today that most of the problems that are to be addressed via Golden Rice and other GMOs can be resolved in matter of days, with the right political will." - Hans Herren, winner of the World Food Prize 1995

"I don't think any of us would disagree that, if an alternative exists to a GE solution, it's to be preferred" - Mr Hodson QC acting on behalf of the Life Sciences Network  at the New Zealand Royal Commission on Genetic Modification 8th  Feb 2001 http://www.gmcommission.govt.nz/inquiry/08FEB01.pdf p3480 of proceedings - line 2