By: Megan Mach, Rebecca Martone, and Kai Chan
Rock crab in sand and eel grass. 2009. Whitney H. Flickr CC-BY-NC-ND-2.0
Coastal and marine ecosystems provide critical living resources (e.g. fisheries) as well as services like water filtration and coastal protection from flooding and storm events. However, environmental degradation from coastal development, pollution, climate change, etc., are dramatically reducing the ability of these systems to thrive. The recognition that these human impacts often interact with one another, and arise from multiple sectors, has catalyzed a shift toward ecosystem-based management as a way to better protect habitats from multiple sources of impacts. Marine managers—from local governments all the way to the Office of the White House’s National Ocean Council—are emphasizing the importance of considering the cumulative impacts of many human activities on the production of ecosystem services.
Quantifying the impact of multiple human activities on an entire ecosystem is no easy task, however. In a recent study published in the journal Ecosystem Services, Megan Mach and Rebecca Martone from the Center for Ocean Solutions, and Kai Chan from the University of British Columbia, found that there are still major research gaps that limit managers' abilities to understand how cumulative human activities affect ecosystems’ capacity to deliver services.
When Mach and her colleagues examined the literature on shellfish and seagrass-dominated estuarine ecosystems, some of the most well-studied ecosystems globally, they found 2380 studies that claimed to link stressors, ecosystems, and ecosystem services. However, only 253 studies linked the stressors back to specific human activities. Furthermore, only 5% of the studies measured the change in the ecosystem’s ability to supply a particular service, and only 1.3%, tested for changes in how the ecosystem delivered benefits to people. The currently available studies are insufficient to measure the full effects of human activities and the subsequent impacts on ecosystem services.
Disentangling which human activity causes a particular environmental change can be difficult, especially when a single impact can be the result of many activities. It is also challenging to identify how much of a given ecosystem service each ecosystem component provides. For example, water filtration as a service is the net activity of many species in a biological community, not a single species, and losses of single organisms or even a population of organisms may not translate into a loss of filtration capacity in a region. Finally, the value of a service depends on the desires and needs of the human beneficiaries. Appraising the trade-offs of ecosystem services will call for research that better integrates human dimensions.
These data gaps make it difficult for managers to evaluate trade-offs between management options. In the absence of complete information, researchers and managers may make generalizations based on studies that provide an incomplete picture of impacts. This is extremely problematic—management approaches require demonstrated proof of harm before responding, but there is enormous potential for uncertainties in the assumptions managers would have to make given the current knowledge gaps.
Although data limitations make it difficult to address the relationships between human activities and ecosystem services, Mach et al. emphasize that scientists have an opportunity to fill these gaps. Determining where to focus scientific and management resources on overcoming this challenge will require collaborative relationships across traditional disciplinary boundaries. But the resultant knowledge such research would provide could prove invaluable to successfully implement ecosystem-based management.
Citation: Mach, Megan E., Rebecca G. Martone, Kai M.A. Chan (2015). Human impacts and ecosystem services: Insufficient research for trade-off evaluation. Ecosystem Services. 16: 112-120.