Understanding variations in ecosystem service provision

The Millennium Ecosystem Assessment defines ecosystem services as the benefits that people derive from ecosystems (MA 2005). It is the natural capital that we rely on for food production, climate stabilization, pollination and drinking water. In the last decade, research on ecosystem services has exploded as academics and practitioners alike are searching for more explicit connections between ecosystems and human well being. New York City’s water supply is the successful adoption of the ecosystem services framework in practice. When water managers were evaluating alternatives for improving drinking water quality, it was found that investing in their natural capital, through watershed management and forest conservation, provided equivalent water quality at only a fraction of the cost of a new filtration plant. The financial savings have been estimated at $6 to $8 billion, plus $300 million per year in maintenance (Chichilnisky & Heal 1998, NRC 2000).

However our dependence on ecosystems has not prevented us from stressing them to the point where we have reduced their capacity to meet our needs (MA 2003). To maintain our ecosystem services intact we must incorporate their value into decision making (Daily et al. 2009). Initially ecosystem valuations measured total economic value (Costanza et al. 1997, Loomis et al. 2000). In a widely cited piece from Nature, Costanza et al. (1997) calculated the total economic value of 17 global ecosystem services to be in the range of USD$16-54 trillion/yr. Yet these estimates of total economic value were of little use to decision makers since most management choices operate at smaller scales and on the margins. That is, decision makers need to understand how the additional protection of an ecosystem will provide additional economic benefits to human populations. Marginal values are essential for evaluating tradeoffs. This recognition inspired research that integrated economic and ecological systems with the purpose of estimating the marginal values of ecosystem services (NRC 2005).

The problem with marginal valuations is that they generally assume a linear relationship between the ecosystem’s condition and the value of the service provided. This linearity does not hold for either ecosystem conditions or for the services provided. Ecologists have documented that ecosystems can fluctuate between alternative states where marginal changes have no impact if thresholds have been passed (Holling 1978). Economic systems also have thresholds whereby costs kick in after a certain point. Thus assuming linearity in our study of ecosystem services is likely to provide misleading information (Barbier et al. 2008). A new consensus is emerging that research on ecosystem services must consider the inherent variability and thresholds that are characteristic of both ecological and economic systems.

Researchers have only recently attempted to understand the stochastic qualities of ecosystem services. Aburto-Oropeza et al. (2008) studied the spatial and temporal fluctuations of fish catch as they related to mangrove conditions, while Koch et al. (2009) studied the irregular protection of coastal property provided by marine vegetation. The scant review of non-linear ecosystem service provision has generated urgent calls for improving our understanding of how ecosystem services fluctuate across space and time (Koch et al. 2009, Kremen et al. 2009).

Aburto-Oropeza, Octavio, Exequiel Ezcurra, Gustavo Danemann, Víctor Valdez, Jason Murray, and Enric Sala. 2008. Mangroves in the Gulf of California increase fishery yields. Proceedings of the National Academy of Sciences (30): 10456-9.

Barbier, Edward B., Evamaria W. Koch, Brian R. Silliman, Sally D. Hacker, Eric Wolanski, Jurgenne Primavera, Elise F. Granek, et al. 2008. Coastal ecosystem-based management with nonlinear ecological functions and values. Science 319: 321-3.

Berrens, R., Ganderton, P. Silva, C. 1996. Valuing the protection of minimum instream flow in New Mexico. Journal of Agricultural Resource Economics. 21:90-104.

Chichilnisky, G. and G. Heal. 1998. Economic returns from the biosphere. Nature 391: 629-630.

Costanza, Robert, Ralph D'Arge, Rudolf de Groot, Stephen Farber, Monica Grasso, Bruce Hannon, Karin Limburg, et al. 1997. The value of the world's ecosystem services and natural capital. Nature (387): 253-260.

Daily, Gretchen C., Stephen Polasky, Joshua Goldstein, Peter M. Kareiva, Harold A. Mooney, Liba Pejchar, Taylor H. Ricketts, James Salzman, and Robert Shallenberger. 2009. Ecosystem services in decision making: Time to deliver. Frontiers in Ecology and the Environment (1): 21-8.

Daily, Gretchen C. 1997. Introduction: What are ecosystem services? In Nature's services: Societal dependence on natural ecosystems., ed. Gretchen C. Daily, 1-19. Washington, D.C.: Island Press.

Holling, C. S. 1978. Adaptive environmental assessment and management. Wiley IIASA international series on applied systems analysis Chichester ; New York: Wiley.

Kremen, Claire, and Richard S. Ostfeld. 2005. A call to ecologists: Measuring, analyzing, and managing Ecosystem services. Frontiers in Ecology and the Environment (3): 540-8.

Koch, Evamaria W., Edward B. Barbier, Brian R. Silliman, Denise J. Reed, Gerardo M. E. Perillo, Sally D. Hacker, Elise F. Granek, et al. 2009. Non-linearity in ecosystem services: Temporal and spatial variability in coastal protection. Frontiers in Ecology and the Environment (1): 29-37.

Loomis, J.B., P. Kent, L. Strange, K. Faush, A. Covich. 2000. Measuring the total economic value of restoring ecosystem services in an impaired river basin: results from a contingent valuation study. Ecological Economics. (33):103-117.

Millennium Ecosystem Assessment. 2005. Ecosystems and human well-being: Current states and trends. Washington DC: Island Press.

National Research Council. 2000. Watershed management for potable water supply: Assessing the New York City strategy. Washington, D.C.: National Academy Press.

National Research Council. 2005. Valuing Ecosystem Services: Toward Better Environmental Decision Making. Washington, D.C.: National Academy Press.