Spatial Subsidies: Quantifying Linkages between Human and Natural Systems with Migratory Species Active

A Task of the Ecosystem Services Assessment and Valuation project.

What Are Spatial Subsidies?

Spatial subsidies result because of mismatches between the location(s) of habitats most important for the survival of migratory species and the location(s) where humans most benefit from the species. For example, migratory ducks are most dependent on productive breeding habitat in the north where relatively few people live. Humans derive benefits from ducks primarily through hunting and wildlife viewing, which occurs largely at stopover sites during the fall migration and in southern winter habitat which are close to areas with many more people. People living in the duck's winter range are therefore receiving benefits derived from summer breeding habitat. In a sense, they are being subsidized by the availability of high-quality habitat further north.

The concept of spatial subsidies allows us to quantify the spatial ecological dependencies of coupled human-natural systems that have developed around migratory species. Quantifying these dependencies will make it possible to:

1. Identify how and where people derive benefit from a migratory species;
2. Establish which habitat locations are most critical for the growth and survival of a migratory population;
3. Determine the extent to which (often distant) critical habitat subsidizes the economic and social wellbeing of people throughout the migratory range of a species;
4. Educate decision-makers and the public about the connections between their livelihoods and/or wellbeing and distant landscapes;
5. Reveal the value of a landscape for the role it plays in supporting migratory species;
6. Resolve conflicts over the sustainable and equitable allocation of exploited migratory species;
7. Facilitate cross-jurisdictional cooperative management of migratory species;
8. Identify the magnitude and potential sources of funding that could be developed for investment in the maintenance of migratory populations;
9. Target conservation funding to those areas most important for maintenance of migratory populations and their ecosystem services;
10. Establish programs to incentivize conservation in ecologically important areas where people derive little to no benefit from migratory species; and
11. Close the feedback loop for coupled human-natural systems involving migratory species.

How Do You Calculate Subsidies?

To quantify spatial subsidies we need a combination of biological and socioeconomic information. On the biological side, we need to know how migratory species depend on the various ecosystems they visit throughout their migration. Spatially explicit population modeling can be used to estimate this proportional dependence, D_S, of a species on different parts of its range (e.g. Wiederholt and others, 2013).

We have a NIMBioS working group, "Estimating area-specific contributions to the population dynamics of migratory species", starting in 2014 to further develop and refine these methods.

On the socioeconomic side we need to know how and where humans benefit from a species. This involves conducting an ecosystem services analysis to estimate the dollar value of different benefits provided by a species, V_S. Benefits provided by migratory species include pollination, pest control, recreation (hunting & viewing), subsistence harvest, existence/bequest values, and others (see our list of publications, below). All sources of value must be collected and/or compiled for each part of the range of a migratory species such that the areas used to estimate economic benefits match the areas used to estimate proportional dependence.

Once estimates for the proportional dependence and ecosystem service value(s) have been obtained, the spatial subsidy, Y, can be estimated using the following equation (Semmens and others, 2011; López-Hoffman and others, 2013):

Y_A = V_SD_SA − V_SA

Where Y_A is the subsidy at location A, V_S is the total value of benefits provided by a species S across its entire range, D_SA is the proportional dependence of the species on location A, and V_SA is the value of benefits provided by the species at location A. Positive values indicate that location A is subsidizing other parts of the migratory range and negative values indicate that it is being subsidized by other areas. When summed across all parts of a migratory species' range, the subsidy necessarily balances out to 0.

Powell Center Working Group—Animal Migration and Spatial Subsidies: Establishing a Framework for Conservation Markets

A grant from the USGS Powell Center for Analysis and Synthesis has allowed us to convene a working group in which we pioneered calculating spatial subsidies for three well-known North American migratory species: northern pintail ducks, monarch butterflies, and Mexican free-tailed bats. These three species provide a wide range of services, from purely aesthetic cultural services to economically important regulatory services. Similarly, a wide range of markets exist for their services, from well-established markets to no markets at all. These species were selected deliberately to further develop and demonstrate the Semmens and others (2011) spatial subsidy approach for three very different types of migratory species.

Early publications from the working group have focused on range-wide, spatially explicit economic valuation of the goods and services provided by each species, and estimating the extent to which the species depends on different parts of its range for survival and reproduction at the population level. Papers presenting our final subsidy calculations for each species and synthesizing lessons learned are anticipated in 2014.

Members of the working group:

• Darius Semmens, Principal Investigator—Research Physical Scientist, USGS, Denver, Colorado
• Laura López-Hoffman, Principal Investigator—Assistant Research Professor, Udall Center for Studies in Public Policy; Assistant Professor, School of Natural Resources and Environment, University of Arizona, Tucson
• Jay Diffendorfer, Principal Investigator—Research Ecologist, USGS, Denver, Colorado
• Amy Russell—Assistant Professor, Department of Biology, Grand Valley State University, Allendale, Michigan
• Brady Mattsson—Independent Researcher, San Francisco Bay Joint Venture and USGS National Wetlands Research Center
• Brice Semmens—Assistant Professor, Scripps Institute of Oceanography, University of California, San Diego
• Gary McCracken—Professor and Department Head, Ecology and Evolutionary Biology, University of Tennessee, Knoxville
• Jim Dubovsky—Central Flyway Representative, U.S. Fish and Wildlife Service, Denver, Colorado
• John Loomis—Professor, Department of Agricultural and Resource Economics, Colorado State University, Fort Collins
• Josh Goldstein—Ecosystem Services Scientist, The Nature Conservancy, Fort Collins, Colorado
• Karen Oberhauser—Associate Professor, Department of Fisheries, Wildlife and Conservation Biology, University of Minnesota, St. Paul
• Ken Bagstad—Research Economist, USGS, Denver, Colorado
• Leslie Ries—Assistant Research Scientist, Department of Biology, University of Maryland, College Park
• Rodrigo Medellín—Professor, Institute of Ecology, Universidad Nacional Autónoma de México
• Ruscena Wiederholt—Postdoctoral Researcher, School of Natural Resources and Environment, University of Arizona, Tucson
• Wayne Thogmartin—Research Statistician, USGS, La Crosse, Wisconsin

References

• Askins, R.A., 1995, Hostile Landscapes and the Decline of Migratory Songbirds: Science, v. 267, no. 5206, p. 1956-1957.
• Brower, L.P., Taylor, O.R., Williams, E.H., Slayback, D.A., Zubieta, R.R., and Ramirez, M.I., 2012, Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk?: Insect Conservation and Diversity, v. 5, no. 2, p. 95-100.
• Kirby, J.S., Stattersfield, A.J., Butchart, S.H.M., Evans, M.I., Grimmett, R.F.A., Jones, V.R., O'Sullivan, John, Tucker, G.M., and Newton, Ian, 2008, Key conservation issues for migratory birds in the world's major flyways: Bird Conservation International, v. 18, p. 49-73.
• Limburg, K.E., and Waldman, J.R., 2009, Dramatic declines in North Atlantic diadromous fishes: BioScience, v. 59, no. 11, p. 955-965.
• Rappole, J.H., and McDonald, M.V., 1994, Cause and effect in population declines of migratory birds: The Auk, v. 111, no. 3, p. 652-660.
• Sanderson, F.J., Donald, P.F., Pain, D.J., Burfield, I.J. and van Bommel, F.P.J., 2006, Long-term population declines in Afro-Palearctic migrant birds: Biol Conserv., v. 131, p. 93-105.
• Sauer, J.R., Hines, J.E. and Fallon, J., 2007, The North American Breeding Bird Survey, results and analysis 1966-2007. Version 10.13.2007: U.S. Geological Survey Patuxent Wildlife Research Centre, Laurel, Maryland.
• Sauer, J.R., Hines, J.E., Fallon, J.E., Pardieck, K.L., Ziolkowski, D.J. Jr., and Link, W.A., 2014, The North American Breeding Bird Survey, Results and Analysis 1966-2012. Version 02.19.2014: U.S. Geological Survey Patuxent Wildlife Research Center, Laurel, Maryland.

Credits for banner image: Northern Pintail: Dave Menke, U.S. Fish and Wildlife Service, Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0) license; Monarch butterfly: Emily Weiser, USGS, Public domain; Colony of bats: Alan Cressler, USGS, Public domain.