State of the Global Phosphorus Cycle

About the Workshop

Roughly a generation ago, environmental scientists began a concentrated effort to document the extent, pace and consequences of human alteration to Earthís major biogeochemical cycles. Early work stressed the links between carbon and climate, sulfur and acid rain, and nitrogen and a suite of environmental changes. For phosphorus, the concern was eutrophication of freshwater and marine ecosystems. Such work put biogeochemistry on the policy map, with some early positive outcomes, such as the reduction in sulfur emissions in the U.S., and the recovery of the Great Lakes. In the case of the carbon and nitrogen cycles, the problems are far from solved, but the last two decades have brought an explosion of scientific knowledge on how - and why - each cycle is changing, at every scale from local to global. As a result, substantive debates on how to mitigate the environmental threats are now happening in multiple sectors of society.

Yet, compared to the state of our knowledge on C and N cycles, phosphorus lags behind. We know humans have dramatically altered the global P cycle (and continue to do so), and we know that changes in P availability can substantially alter the structure and function of both terrestrial and aquatic ecosystems. We also know that interactions among the C, N and P cycles are pervasive, and often critical to understand if one wants to predict the behavior of any one of these elements. For example, soil P availability is likely to be a significant determinant of C storage (or loss) in both intact and converted tropical forests. Likewise, P availability can regulate inputs of reactive N to the biosphere, as well as their eventual fate. However, while we know humans are changing the P cycle, we lack a quantitative picture at regional scales of how much, how fast, and in what ways. Such information is essential not only for predicting well-recognized consequences of P enrichment, such as aquatic eutrophication, but also for understanding the ways in which the global C and N cycles will continue to evolve. Finally, useful reserves of reactive P are finite, and the long term sustainability of intensive agricultural systems depends on the careful management of P reserves.

A regionally-specific assessment of the global phosphorus cycle is needed. This activity was identified as a priority at the recent AGCI Workshop ìManaging the Global N and P Cycles.î Like nitrogen, the majority of human-driven changes to the P cycle are linked to modern agriculture, and thus prior assessments of the N cycle will be enormously helpful to the efforts for P. For example, the rise of globalized economies and the biofuel industry over the last two decades have caused massive shifts in agriculture, causing new regional hotspots for reactive N, and a steep rise in global trade of N-containing commodities. We expect to find similar dynamics for P, and can use much of the information assembled for the N assessments as a basis for our proposed work.

The goal of this workshop was to finalize a strategy to complete the assessment, to identify components of the work that individual participants would lead, and to galvanize the entire process.

      Roster

Elena Bennett Tim Crews Kimberly Epps Gabriel Filippelli Stephen  Porder David Schindler Meagan Schipanski Philip  Taylor Alan Townsend

MORE INFO Additional roster information is available via PDF: View detailed roster Looking for someone specific? Use our past participant search to search scientists by name, organization, country, or expertise. Search scientists

Agenda

Thursday, 1st October
10:00 AM		Global P Cycle: The Terrestrial Realm In his talk, Stephen Porder highlights some of the major uncertainties associated with the terrestrial phosphorus cycle. Human society has been built on the massive alteration of the Earth's biogeochemical cycles, particularly those of carbon (from fossil fuel burning), nitrogen and phosphorus (from fertilizer use). Unlike fossil fuels, which can be replaced by cleaner fuels, and nitrogen fertilizers, which can be replaced by legumenous crops, phosphorus fertilizer comes from highly concentrated ore that is limited in amount and spatial distribution. While productivity in natural systems is often limited by phosphorus, humans have temporarily overcome this limitation by mining this ore. However in in the future it is likely that absent major changes in the way we use our farmlands, we will ulitmately return to a population size limited by phosphorus.  View Powerpoint Slides [PDF]		Stephen  Porder
11:00 AM		Global P Cycle: The Freshwater Realm Many scientists have assessed humanity's impact on the global phosphorus (P) cycle. These assessments have taken many forms -- some have examined changes in outflow of dissolved P in the world's major rivers. Others have looked at the changes in cycling of particulate P or increases in fertilizer use. In this lecture, Dr. Bennett examines some of these assessments of the global P cycle, including her own 2001 assessment of soil P accumulation in current and pre-mining times. She concludes from this analysis that global, and even regional, P budgets hide spatial variability and shows results of a spatially-explicit P budget for the world. This budget shows P accumulation in some areas, such as the Netherlands, China, and India, and depletion in other areas, such as the midwestern United States, much of Africa, and parts of Europe  View Powerpoint Slides [PDF]		Elena  Bennett
11:45 AM		Global P Cycle: The Marine Realm  View Powerpoint Slides [PDF]		Gabriel  Filippelli
2:00 PM		P Weathering Rates  View Powerpoint Slides [PDF]		Gabriel  Filippelli
2:45 PM		P Limitation in Terrestrial Ecosystems  View Powerpoint Slides [PDF]		Cory  Cleveland
3:30 PM		Coherent stoichiometric control over N and P accumulation from soils to the sea  View Powerpoint Slides [PDF]		Philip  Taylor
6:30 PM		Walter Orr Roberts Public Lecture: Agriculture After Norman Borlaug Norman Borlaug (1914-2009), the "father of the Green Revolution," is said to have affected more people's lives than any one human in the 20th century, and yet he has almost no name recognition. In the 1960s, Borlaug led the scientific crusade to breed high yielding wheat, which required prodigious applications of synthetic fertilizers. In this lecture, Dr. Tim Crews sets the achievements of Norman Borlaug in context by exploring how humanity managed soil fertility before Borlaug's Green Revolution, and he unfolds some fundamental sustainability challenges facing humanity in Borlaug's wake. In the conclusion, Crews addresses whether organic agriculture can feed the world.   Watch Video    View Powerpoint Slides [PDF]		Tim  Crews

Friday, 2nd October
8:30 AM		P movement through the transport of human food and animal feed Efforts to reduce phosphorus losses from agricultural systems have primarily focused on improving on-farm phosphorus use efficiency. Often overlooked are the phosphorus losses that occur between crop harvest and food consumption, which can be of a similar magnitude to on-farm losses. This talk provides an overview of global phosphorus flows through livestock production systems and human consumption. The opportunities for recycling phosphorus-containing "wastes" from the food chain is dependent on the proximity of crop production and consumption. The spatial separation of croplands requiring P fertilizers and areas producing wastes is increasing due to growth in global trade and the continued industrialization of livestock production systems.   View Powerpoint Slides [PDF]		Meagan  Schipanski
9:15 AM		P Fertilization  View Powerpoint Slides [PDF]		Tim  Crews
10:00 AM		Eutrophication of lakes cannot be controlled by reducing Nitrogen input  View Powerpoint Slides [PDF]		David  Schindler

Saturday, 3rd October
8:30 AM		What regulates recovery time of water bodies following cessation of P loading?  View Powerpoint Slides [PDF]		Kimberly  Epps

Documents

Background Materials

	The pre-Colombian footprint on terrestrial nutrient cycling in Costa Rica: Insights from phosphorus in a lake sediment record Journal of Paleolimnology (2009) The impact of pre-Columbian subsistence agriculture on soil nutrient cycling in the American tropics is poorly quantified. Here we describe our use of a chemical sequential extraction technique adapted from soil fertility research to discern geochemical fractions of phosphorus (P) in lake sediments that serve as proxies for landscape-scale soil nutrient status. We propose that the entire P geochemical record is dominated by human-induced alteration of the soil nutrient cycles via agriculture and occupation, and that the only interval that reveals the "natural" nutrient status in the region is the short interval when the site is abandoned and surrounding forests regrow.  Filippelli, G. et al. " The pre-Colombian footprint on terrestrial nutrient cycling in Costa Rica." Journal of Paleolimnology. Published online, 1 September 2009. (Contributed by Gabriel Filippelli)
	A Safe Operating Space for Humanity Nature (2009) Identifying and quantifying planetary boundaries that must not be transgressed could help prevent human activities from causing unacceptable environmental change, argue Johan Rockstrom and colleagues. Rockstrom, Johan. "A Safe Operating Space for Humanity." Nature 461 (24 September 2009): 472-475. (Contributed by Tim Crews)
	Chemical weathering, mass loss, and dust inputs across a climate by time matrix in the Hawaiian islands Earth and Planetary Science Letters (2007) We determined the total mass loss and rate of chemical weathering from three minimally eroded, Hawaiian lava flows that are 10, 170, and 350 ka old. Although Hawaii is one of the least dusty places in the northern hemisphere, dust inputs reached 82% of the total mass loss from the weathering zone at some sites, and averaged 30% on the 170 ka flow. This highlights the potential importance of dust as a component of observed weathering fluxes from catchments worldwide. Porder, Stephen, et al. "Chemical weathering, mass loss and dust inputs across a climate by time matrix in the Hawaiian Islands." Earth and Planetary Science Letters 258 (2007): 414-427. (Contributed by Stephen Porder)
	Distribution of phosphorus resources between rich and poor countries: The effect of recycling Ecological Economics (2008) Phosphorus (P) is an essential input into agriculture with no substitute. Thus internationaland intertemporal P allocations greatly impact food security which requires increased foodproduction for a growing world population. As high quality phosphorus mines are beingdepleted, recycling gains importance and developed countries explore new technologies forP recycling. We analyse the effects of P recycling in developed countries on global extractionof rock phosphates and the imports of developing countries. We build a resource extractionmodel for a competitive fertilizer market that reflects the fact that most developed countrieshave P-saturated soils while soils in many developing countries are P-deficient. Our modelextends a simple cake eating problem. We consider two types of countries that differ indemand and recycling options. We find that P recycling in developed countries does not onlyprolong the resource life-time, but it also increases the developing counties' share of theresource. Weikard, Hans-Peter, Demet Seyhan. "Distribution of phosphorus resources between rich and poor countries: The effect of recycling." Ecological Economics 68 (2009): 1749-1755. (Contributed by Tim Crews)
	Ecological Engineering: Lessons from China Ambio (1993) Economic development and urbanization worldwide have led to many pollution problems as a result of growing input to the environment of organic wastes and inorganic nutrients. Even the developed countries have not been able to solve this problem satisfactorily. The situation is especially problematical in developing countries where raw wastes are disrupting the coastal ecosystems that are the main source of food protein. This article describes how these problems are addressed in China, using aquaculture and ecological engineering not only to solve waste problems, but also to optimize food and energy production by completely recycling wastes in integrated farming systems. Chan, George L. "Ecological Engineering: Lessons from China." Ambio 22, no. 7 (Nov. 1993): 491-494. (Contributed by Cory Cleveland)
	Efficiency of soil and fertilizer phosphorus use: Reconciling changing concepts of soil phosphorus behavior with agronomic information Food and Agriculture Organization (2008) This report reviews, analyses and synthesizes information on the efficient useof soil and fertilizer P. It presents information on the plant availability of soiland fertilizer P, with an emphasis on soil-plant interactions. The focus is on thechanging concepts of the behavior of both soil and fertilizer P and on the need todefine and assess their recovery and, thus, P-use efficiency, more appropriately. Thereport also outlines strategies for improving P-use efficiency.The main conclusion of this report is that the efficiency of fertilizer P use isoften high (up to 90 percent) when evaluated over an adequate time scale using thebalance method. Syers, J.K., A.E. Johnston, and D. Curtin. Efficiency of soil and fertilizer phosphorus use. Rome: Food and Agriculture Organization, 2008. (Contributed by Tim Crews)
	Eutrophication of lakes cannot be controlled by reducing nitrogen input PNAS (2008) Lake 227, a small lake in the Precambrian Shield at the Experimental Lakes Area (ELA), has been fertilized for 37 years with constantannual inputs of phosphorus and decreasing inputs of nitrogen totest the theory that controlling nitrogen inputs can control eutrophication.For the final 16 years (1990-2005), the lake wasfertilized with phosphorus alone. Reducing nitrogen inputs increasinglyfavored nitrogen-fixing cyanobacteria as a response bythe phytoplankton community to extreme seasonal nitrogen limitation.Nitrogen fixation was sufficient to allow biomass to continueto be produced in proportion to phosphorus, and the lakeremained highly eutrophic, despite showing indications of extremenitrogen limitation seasonally. To reduce eutrophication, the focusof management must be on decreasing inputs of phosphorus. Schindler, David et al. "Eutrophication of lakes cannot be controlled by reducing nitrogen input." PNAS 105, no. 32 (12 August 2008): 254-258. (Contributed by David Schindler)
	Impacts of increasing anthopogenic soluble iron and nitrogen deposition on ocean biogeochemistry Global Biogeochemical Cycles (2009) This article presents results from transient sensitivity studies with the BiogeochemicalElemental Cycling (BEC) ocean model to increasing anthropogenic atmosphericinorganic nitrogen (N) and soluble iron (Fe) deposition over the industrial era. Krishnamurthy, Apama et al. "Impacts of increasing anthopogenic soluble iron and nitrogen deposition on ocean biogeochemistry." Global Biogeochemical Cycles 23 (29 August 2009). (Contributed by Tim Crews)
	Magnitudes and Sources of Dissolved Inorganic Phosphorus Inputs to Surface Freshwaters and the Coastal Zone: A New Global Model Unpublshed (0000) As a limiting nutrient in aquatic systems, phosphorus (P) plays an important role in controlling freshwater and coastal primary productivity and ecosystem dynamics, increasing frequency and severity of harmful and nuisance algae blooms and hypoxia, as well as contributing to loss of biodiversity. Although dissolved inorganic P (DIP) often constitutes a relatively small fraction of the total P pool in aquatic systems, its bioavailability makes it an important determinant of ecosystem function. Here we describe, apply, evaluate, and interpret an enhanced version of the Global NEWS-DIP model: NEWS-DIP-Half Degree (NEWS-DIP-HD). Harrison, John A. et al. "Magnitudes and Sources of Dissolved Inorganic Phosphorus Inputs to Surface Freshwaters and the Coastal Zone: A New Global Model." Unpublished. (Contributed by Tim Crews)
	Nitrogen and phosphorus budgets for a tropical watershed impacted by land use: Guayas, Ecuador Biogeochemistry (2006) Large-scale changes in land use are occurring in many tropical regions, with significant impacts on nitrogen and phosphorus biogeochemistry. In this study we examine the relationships between land use, anthropogenic nutrient inputs, and riverine nutrient exports in a major agricutural watershed of the Pacific coast of South America, the Guayas River basin of Ecuador. Borbor-Cordova, Mercy J, Elizabeth W. Boyer, William H. McDowell, and Charles A. Hall. "Nitrogen and phosphorus budgets for a tropical watershed impacted by land use: Guayas, Ecuador." Biogeochemistry 79: 135-161. (Contributed by Cory Cleveland)
	On the Fate of Atmospheric Nitrogen PNAS (2009) This article provides a synthesis of literature values to trace the fate of 150 Tg/yr anthropogenic nitrogen applied by humans to the Earth's land surface. Schlesinger, William H. "On the Fate of Anthropogenic Nitrogen." PNAS 106, no. 1 (6 January 2009): 203-208. (Contributed by Philip Taylor)
	Persistence of Rock-Derived Nutrients in the Wet Tropical Forests of La Selva, Costa Rica We used strontium isotopes and analysis of foliar and soil nutrients to testwhether erosion can rejuvenate the supply of rock-derived nutrients in the lowland tropicalrain forest of La Selva, Costa Rica. We expected that these nutrients would be depletedfrom soils on stable surfaces, a result of over one million years of weathering in situ. Infact, trees and palms in all landscape positions derive a relatively high percentage (40%)of their strontium from bedrock, rather than atmospheric, sources. The fraction that is rockderivedincreases on slopes, but with no detectable effect on plant macronutrient concentrations.These results differ from those in a similar ecosystem on Kauai, Hawaii, whereplants on uneroded surfaces derive almost all of their foliar Sr from atmospheric, ratherthan bedrock, sources. The results from La Selva challenge the assumption that tropicalOxisols in general have low nutrient inputs from bedrock, and support the hypothesis thaterosion can increase the supply of these nutrients in lower landscape positions Porder, Stephen. "Persistence of Rock-Derived Nutrients in the Wet Tropical Forests of La Selva, Costa Rica." Ecology 87, no. 3 (March 2006): 594-602. (Contributed by Stephen Porder)
	Phosphorus in the Environment: Natural Flows and Human Interferences Annual Review of Energy Environment (2000) Phosphorus has a number of indispensable biochemical roles, but it doesnot have a rapid global cycle akin to the circulations of C or N. Natural mobilization ofthe element, a part of the grand geotectonic denudation-uplift cycle, is slow, and lowsolubility of phosphates and their rapid transformation to insoluble forms make theelement commonly the growth-limiting nutrient, particularly in aquatic ecosystems.Human activities have intensified releases of P. By the year 2000 the global mobilizationof the nutrient has roughly tripled compared to its natural flows: Increased soil erosionand runoff from fields, recycling of crop residues and manures, discharges of urbanand industrial wastes, and above all, applications of inorganic fertilizers (15 milliontonnes P/year) are the major causes of this increase. Global food production is nowhighly dependent on the continuing use of phosphates, which account for 50-60% ofall P supply; although crops use the nutrient with relatively high efficiency, lost P thatreaches water is commonly the main cause of eutrophication. This undesirable processaffects fresh and ocean waters in many parts of the world. More efficient fertilizationcan lower nonpoint P losses. Although P in sewage can be effectively controlled, suchmeasures are often not taken, and elevated P is common in treated wastewater whoseN was lowered by denitrification. Long-term prospects of inorganic P supply and itsenvironmental consequences remain a matter of concern. Smil, Vaclav. "Phosphorus in the Environment: Natural Flows and Human Interferences." Annual Review of Energy Environment 2000: 53-88. (Contributed by Tim Crews)
	Phosphorus: Global Transfers Although relatively rare in the biosphere, phosphorus (P)plays several key roles in the chemistry of life, above all dueto its presence in nucleic acids (deoxyribonucleic acid, DNAand ribonucleic acid, RNA) and in adenosine triphosphate,the life's carrier of energy. Phosphorus - unlike carbon, C,nitrogen, N and sulfur, S - does not form any long-livedatmospheric compounds and hence its global cycle is justa part of the grand, and slow, process of denudation andgeotectonic uplift. But on a small scale the element is rapidlyrecycled between organic and inorganic forms in soils andwater bodies. Human activities now annually move morethan four times as much phosphorus as did the naturalprocesses during the pre-agricultural era. Smil, Vaclav,"Phosphorus: Global Transfers." In Encyclopedia of Global Environmental Change. Ian Douglas, editor. Chichester: John Wiley & Sons, 2002. (Contributed by Tim Crews)
	Terrestrial Phosphorus Limitation: Mechanisms, Implications, and Nitrogen-Phosphorus Interactions Nutrient limitation to primary productivity and other biological processes is widespread in terrestrial ecosystems, and nitrogen (N) and phosphorus (P) are the most common limiting elements, both individually and in combination. Mechanisms that drive P limitation - and their interactions with the N cycle - have received less attention than mechanisms causing N limitation. We identify and discuss 6 mechanisms that could drive P limitation in terrestrial ecosystems: depletion-driven limitation; soil barriers that prevent access to P; transactional limitation, in which weathering of P-containing minerals does not keep pace with the supply of other resources; low-P parent materials; P sinks; and anthropogenic changes that increase the supply of other resources (often N) relative to P. Vitousek, Peter M., Stephen Porder, Bejamin Z. Houlton, Oliver A. Chadwick. "Terrestrial Phosphorus Limitation: Mechanisms, Implications, and Nitrogen-Phosphorus Interactions." Working Paper. (Contributed by Tim Crews)
	The Global Phosphorus Cycle: Past, Present, and Future Elements (2008) The cycling of phosphorus, a biocritical element in short supply in nature,is an important Earth system process. Variations in the phosphorus cyclehave occurred in the past. For example, the rapid uplift of the Himalayan-Tibet Plateau increased chemical weathering, which led to enhanced input ofphosphorus to the oceans. This drove the late Miocene "biogenic bloom."Additionally, phosphorus is redistributed on glacial timescales, resulting fromthe loss of the substantial continental margin sink for reactive P during glacialsea-level lowstands. The modern terrestrial phosphorus cycle is dominated byagriculture and human activity. The natural riverine load of phosphorus hasdoubled due to increased use of fertilizers, deforestation and soil loss, andsewage sources. This has led to eutrophication of lakes and coastal areas, andwill continue to have an impact for several thousand years based on forwardmodeling of human activities. Filippelli, Gabriel. "The Global Phosphorus Cycle: Past, Present, and Future." Elements 4: 89-95. (Contributed by Gabriel Filippelli)
	The Oceanic Phosphorus Cycle Chemical Reviews (2007) Phosphorus availability can impact primary productionrates in the ocean as well as species distribution andecosystem structure. In some marine and estuarine environments,P availability is considered the proximal macronutrientthat limits primary production. Specifically, inrecent years it has been recognized that phosphorus limitationin the ocean may be more prevalent than previously thought. Paytan, Adina and Karen McLaughlin. "The Oceanic Phosphorus Cycle." Chemical Reviews 107, vol. 2 (2007), 563-576. (Contributed by Tim Crews)
	The Story of phosphorus: Global Food Security and Food for Thought Global Environmental Change (2008) Food production requires application of fertilizers containing phosphorus, nitrogen and potassium onagricultural fields in order to sustain crop yields. However modern agriculture is dependent onphosphorus derived from phosphate rock, which is a non-renewable resource and current globalreserves may be depleted in 50-100 years. While phosphorus demand is projected to increase, theexpected global peak in phosphorus production is predicted to occur around 2030. The exact timing ofpeak phosphorus productionmight be disputed, however it is widely acknowledged within the fertilizerindustry that the quality of remaining phosphate rock is decreasing and production costs are increasing.Yet future access to phosphorus receives little or no international attention. This paper puts forward thecase for including long-term phosphorus scarcity on the priority agenda for global food security.Opportunities for recovering phosphorus and reducing demand are also addressed together withinstitutional challenges. Cordell, Dana et al. "The Story of Phosphorus: Global Food Security and Food for Thought." Global Environmental Change 19 (2009): 292-305. (Contributed by Tim Crews)