Human alteration of the global nitrogen and phosphorus soil balances

Human alteration of the global nitrogen and phosphorus soil balances

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Unformatted text preview: Human alteration of the global nitrogen and phosphorus soil balances for the period 1970–2050 A. F. Bouwman, 1,2 A. H. W. Beusen, 1 and G. Billen 3 Received 19 May 2009; revised 25 August 2009; accepted 9 September 2009; published 18 December 2009. [ 1 ] The Millennium Ecosystem Assessment scenarios for 2000 to 2050 describe contrasting future developments in agricultural land use under changing climate. Differences are related to the total crop and livestock production and the efficiency of nutrient use in agriculture. The scenarios with a reactive approach to environmental problems show increases in agricultural N and P soil balances in all developing countries. In the scenarios with a proactive attitude, N balances decrease and P balances show no change or a slight increase. In Europe and North America, the N balance will decline in all scenarios, most strongly in the environment-oriented scenarios; the P balance declines (proactive) or increases slowly (reactive approach). Even with rapidly increasing agricultural efficiency, the global N balance, ammonia, leaching and denitrification loss will not decrease from their current levels even in the most optimistic scenario. Soil P depletion seems to be a major problem in large parts of the global grassland area. Citation: Bouwman, A. F., A. H. W. Beusen, and G. Billen (2009), Human alteration of the global nitrogen and phosphorus soil balances for the period 1970–2050, Global Biogeochem. Cycles , 23 , GB0A04, doi:10.1029/2009GB003576. 1. Introduction [ 2 ] During the past five decades, global population, food production, and energy consumption have increased approx- imately 2.5-fold, threefold and fivefold, respectively [ FAO , 2008; Gru ¨bler et al. , 1995]. Through activities such as fertilizer use, fossil fuel consumption and the cultivation of leguminous crops, humans have more than doubled the rate at which biologically available nitrogen (N) enters the terrestrial biosphere compared to preindustrial levels [ Galloway et al. , 2004]. The global phosphorus (P) cycle has also been altered by human activity. Mining of phos- phate rock and subsequent production and use as fertilizer, detergent, animal feed supplement and other technical uses has more than doubled P inputs to the environment over natural, background P from weathering [ Mackenzie et al. , 1998; Tiessen , 1995; United States Geological Survey , 2008]. [ 3 ] The changes in global nutrient cycles have had both positive and negative effects. The increased use of N and P fertilizers has allowed for producing the food necessary to support the rapidly growing human population [ Galloway and Cowling , 2002]. However, significant fractions of the anthropogenically mobilized N and P in watersheds enter groundwater and surface water and are transported through freshwater to coastal marine systems. This has resulted in numerous negative human health and environmental impacts such as groundwater pollution, loss of habitat and biodiver- sity, an increase in frequency and severity of harmful algal...
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Human alteration of the global nitrogen and phosphorus soil balances

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