Phosphorus: Past and Future

Abstract

In Phosphorus, Jim Elser (limnologist) and Phil Haygarth (soil scientist) provide an in-depth look at phosphorus-related barriers to sustainable agriculture. The main question they address is: How can societies continue to feed the planet's human inhabitants without increasing the quantity of phosphorus flowing into aquatic ecosystems or compromising the availability of the raw material from which the bulk of this nutrient is obtained? Elser and Haygarth, writing as scientists to a broad audience, seek to provide the context, technical and otherwise, needed to productively engage in phosphorus-related policy discussions.After an introductory overview (titled “Phosphorus Knowing”), the authors provide a solid discussion of the chemical, biological, and dietary aspects of phosphorus (in chapters titled “Phosphorus Becoming,” “Phosphorus Living,” and “Phosphorus Feeding”). They then examine the changes in global and regional flows of phosphorus that occurred in the transition to industrial agriculture (“Phosphorus Growing”). Next, Elser and Haygarth turn their attention to how nonpoint sources of phosphorus from agriculture threaten the health of aquatic systems (“Phosphorus Polluting”). Finally, they examine the availability of phosphorus rock as a raw material and what a sustainable system for delivering phosphorus to agricultural systems might look like (“Phosphorus Awakening,” “Phosphorus Reducing,” “Phosphorus Recycling,” and “Phosphorus Sustaining”).The strength of Phosphorus lies in the ability of the authors to examine various aspects of the problem in a way that avoids oversimplification. In preindustrial agriculture, soils generally maintained an adequate supply of phosphorus through the gradual weathering of phosphorus compounds from rocks or from the annual deposit of phosphorus-rich silt in river valleys. However, with the mid-twentieth-century dissemination of industrial agriculture, inputs of market-based fertilizers became crucial to achieving the high crop yields people now take for granted. The main raw material for the phosphorus component of these fertilizers is phosphate rock, which is likely to become more expensive in the future as easily accessible deposits of this resource decrease. Furthermore, as the quantity of phosphorus compounds added to soils has increased, so has the amount flowing into adjacent bodies of water, often resulting in problematic algal blooms.Elser and Haygarth tell this story from the perspective of scientists who have worked on phosphorus-related pollution problems over the course of several decades. Indeed, the book takes on something of a memoir style when the authors discuss their involvement in research projects associated with phosphorus-related pollution concerns and, more broadly, advancing the sustainability of practices for delivering phosphorus to agricultural systems. For example, they describe a shift from a general conception that “phosphorus does not leach from the soil,” which the authors were taught as undergraduates, to an understanding that heavy rainstorms can result in the erosion of enough soil (along with the attached phosphorus) to cause problems in adjacent waterways (89). They also discuss their involvement in a research network in which participants have made it their mission to focus on sustainability-related issues involving phosphorus.The use of a first-person point of view allows Elser and Haygarth to communicate the excitement they felt as they and their colleagues began to study phosphorus-related problems from a holistic earth systems perspective. In the chapter “Awakening,” they describe how confusion over the difference between reserves of phosphorus rock (i.e., material able to be profitably extracted at current prices) and deposits of the resource (i.e., material available to be extracted if prices rise) initially led to discussions among scientists about “peak phosphorus” and the possibility of running out of this resource in a few decades (114). However, as the difference between reserves and deposits of this resource became clear, the scientists reframed their interest, focusing less on the narrow issue of supply and more on the question of long-term sustainability.The chapters on actions needed to develop a sustainable system for delivering phosphorus to agricultural systems are uneven. On one hand, they insightfully describe what a sustainable phosphorus system for agriculture might look like in terms of the efficient use of material. On the other hand, ideas about how to construct the political economy needed to encourage movement in the desired direction is lacking. In this area, one can see opportunities for Elser and Haygarth to collaborate with social scientists who are examining efforts to address complex sociotechnical problems through approaches such as participatory and transdisciplinary research.