Ecosystem Status Report for the Northeast Large Marine Ecosystem
It is widely recognized that the management of ocean resources needs to be done using an ecosystem based approach, using methods and strategies that treat the ecosystem as a whole and integrates our knowledge of all levels of the ecosystem from physical forcing to the behavior of top predators including man (Belgrano and Fowler 2011; Christensen and Maclean 2011; Link 2010). In order to assess the status and trends of these socio-ecological systems and to evaluate the impact of different stressors, appropriate metrics must be identified and their overall utility for management validated. These metrics should be broadly representative of forcing factors and associated socio-ecological system states or processes. We designate the most informative and integrative metrics as indicators. Indicators can be broadly classified into natural and anthropogenic drivers, resulting pressures, and system states. For our purposes, we identify drivers as forcing factors such as climate, human population size and economic value underlying a constellation of pressures exerted on the system. These pressures include human‐related impacts on the ocean sub-system such as removal of living marine resources through harvesting, as well as shipping, pollution, and impacts to the coastal zone such as habitat loss. Climate related pressures on the ocean ecosystem include changes in atmospheric and oceanographic processes directly or indirectly affecting marine life. Within the socio-economic sub-system, ecological impacts include changes in levels of marine species biomass available for harvest, and resultant impacts on income streams to harvesters, processers, marine supply companies and communities. These, along with climate-related impacts on marine species and changes in storm frequency and intensity, affect communities and industries along the coast and elsewhere in the region, the US and the world – given the globalization of marine species trade. Developing a greater understanding of the feedback loops that exist between human behavioral responses to a changing ecosystem and to the state of the socio-ecological system overall is an integral component of this process. Here, we update our earlier evaluations of the status of the Northeast U.S Continental Shelf Large Marine Ecosystem (EcoAP 2009; EcoAP 2012) and expand its focus to include further information on ecological subregions of the shelf and more details on the socio-economic portion of the system.
The Northeast U.S. Continental Shelf Large Marine Ecosystem (NES LME) provides a range of key ecosystem services: supporting (e.g. nutrient cycling and primary production), provisioning (e.g. food and pharmaceuticals), regulating (e.g. carbon sequestration and climate regulation) and cultural (e.g. spiritual inspiration, recreation and scientific research). It supports communities, industries, ecosystems, and individuals. It has supported important commercial and recreational fisheries, and recreational activities. This highly productive region has experienced significant structural changes over the last several decades, both in bio-ecological and socio-economic terms. Heavy exploitation, increasing climate variability, increasingly restrictive management measures, increasingly volatile economic cycles, and urban and coastal population growth have greatly impacted all aspects of the socio-ecological system of the Shelf. Emerging evidence for important changes in physical forcing and ecological response in relation to climate variability in the North Atlantic further highlights the need to address the broad suite of natural and anthropogenic drivers at work in the system.
Within the marine ecosystem, we distinguish external physical pressures representing large‐scale ocean‐atmospheric processes affecting this system from internal physical pressures representing local or regional physical manifestations of these broader pressures. Within the socio-economic marine-related system we then identify indicators of both socio-economic and ecological pressures and their impacts. We next describe how the socio-ecological system state is potentially affected by these drivers and associated pressures, with a focus on holistic or integrative metrics of system condition. State variables include metrics such as the abundance of different species groups, measures of biological and economic productivity and measures of economic value and community vulnerability. Our objective is to characterize changes in the system state variables in response to forcing mechanisms associated with a spatially defined ecosystem. An understanding of the inter‐relationships among drivers, pressures, and states is an essential prerequisite to moving toward a place‐based, socio-ecological approach to management.
Part of this place‐based approach involves the recognition that the Northeast U.S. Continental Shelf Large Marine Ecosystem is composed of different regions with distinct patterns in oceanographic characteristics, primary production and fish distribution, among other factors. The NES LME has been divided into a set of Ecological Production Units (EPUs) based on analysis of physiographic and lower trophic level datasets (Fogarty et al. in review) (Figure 1.1). Four primary subunits or EPUs were identified: Gulf of Maine, Scotian Shelf, Georges Bank, and Mid‐Atlantic Bight. Additionally, primary subunits can be further divided, if appropriate, into nearshore and shelf break special consideration areas (denoted as white boundaries in Figure 1.1). The boundaries of the EPUs are open, and in our model formulations we permit movement of water, organisms and human vessels across them. These EPUs therefore provide a starting point for spatial considerations of ecosystem based management in the NES LME and are useful in framing the analyses presented in this report.
Human communities also involve place-based components, in terms of residence, port of landing, and preferred fishing grounds. Within US fisheries management, in fact, the Magnuson–Stevens Fishery Conservation and Management Act requires considerations of place-based communities on land, as well as (when appropriate to assessing the impacts of regulations) communities based on gear group and target species. One of the concerns of the ESR will be to connect these human land and sea-based communities to the processes critical to assessing the status of the marine socio-ecological system.
We have seen unprecedented changes in the physical environment and biological communities of the Northeast Shelf this past year. The extent of these changes have been so large as to pose the question of whether the Northeast Shelf ecosystem has entered into a new regime? Many marine and terrestrial ecosystems have been described as changing between regimes, changes that carry significant societal consequences (Crepin et al. 2012). A shift in regime is characterized as being a large, rapid change in the structure and function of a system, and importantly, a change that persists. North Pacific ecosystems have oscillated between regimes that control physical conditions and resource species productivity in concordance with the Pacific Decadal Oscillation (Mantua et al. 1997). Strictly speaking, the North Atlantic does not have a counterpart system; oscillations between ecosystem states in the North Atlantic have been more gradual and associated with basin scale forcing like the North Atlantic Oscillation or Atlantic Multidecadal Oscillation (Hurrell and Deser 2009; Nye et al. 2013). However, as will be described in this report, a number of the properties of the Northeast Shelf ecosystem shifted dramatically in 2012. Figure 1.2 shows the mean annual sea surface temperature for the Northeast Shelf with the results of a regime shift algorithm superimposed on the data (the red line). A shift would appear to be have been detected in 2012; however, it is premature to call the change in conditions in 2012 a regime shift. There are many statistical techniques used to detect the transition between regimes, and varied opinions on which of these is the appropriate methodology. Not all these methods would suggest a regime shift occurred in 2012. Furthermore, the change in conditions only satisfies half the regime shift definition, we do not know if these conditions will persist. If we are entering a new regime, it will undoubtedly impact the structure and function of the ecosystem and the goods and services the ecosystem provides, making monitoring key elements of the ecosystem that much more important.