Approximately 2,270 species are listed as endangered or threatened under the Endangered Species Act (ESA). At-risk species are vulnerable to becoming listed as endangered or threatened under the ESA.
Populations are often spatially structured. Understanding the effects of spatial structures such as sources and sinks, can be critical for successfully managing at-risk species. A SERDP-funded project led by Dr. Joshua Lawler at the University of Washington worked to develop an understanding of the relative importance of the factors that influence source-sink dynamics in general. Specifically, the team explored the implications of source-sink dynamics for the management of the endangered black-capped vireo (Vireo atricapilla).
Project results have been very beneficial to the Department of Defense (DoD) natural resource managers because they indicate that sinks can be beneficial in systems with rapid population decline. Interestingly, sinks may be superfluous in stable, robust source-sink systems. Sinks can also compromise regional population persistence if they are black-hole sinks (with little or no emigration) and make variable contributions to populations in systems with pseudo-sinks and complex dynamics.
DoD managers are using these insights to avoid the false assumption that sinks are always detrimental to populations. This insight allows the managers to weigh case-specific factors such as population size and volatility, rate of decline, inter-population movement, landscape configuration, and density dependence to make targeted and adaptive management decisions. In addition, the project provided black-capped vireo managers on and off Fort Hood, Texas with a tool (in the form of a parameterized simulation model) to assess the potential effects of different management and climate change scenarios on the vireo across its range.
You are invited to gain a deeper understanding of this recently completed multi-step project by reading the project’s final report which is available to all on the SERDP & ESTCP website.