Emergence of ecological networks

Ecosystems have changed more in the past 50 years than at any time in human history, according to the Millennium Ecosystem Assessment (www.MAweb.org). Many of the most important changes are nonlinear and hard to reverse. Thus, the emergence of big ecological changes from seemingly local events, known as “greenlash”, underlies many of the ecological surprises that we face today. Such disparate phenomena as rising flood frequency, persistent drought, emergence or re-emergence of pandemic disease, harmful invasions of exotic organisms, and pollutant magnification in ecosystems are examples. Greenlash involves contagious spread from local to continental scales, with the most extreme impacts in zones of convergence, where multiple drivers come together. Understanding greenlash requires a new kind of social–ecological science that builds on insights from biogeochemistry, demography, geography, hydrology, landscape ecology, and other disciplines to synthesize new perspectives. New phenomena can emerge in science as well as in ecosystems. Research challenges posed by non-linear or cross-scale phenomena are being identified and understood by new networks of environmental scientists. The process is driven by those who recognize the need for novel approaches to study the connections among local, regional, and continental change. Some networks are bootlegged from existing funding, and others are funded by agencies or foundations that perceive the need to understand multi-scale ecological change and monitor the factors that cause it. The power of the networks derives from strong intellectual support by a variety of scientists from many disciplines, who are motivated by the excitement and importance of the research questions. Now, new networks are being developed and the older networks are re-organizing into “networks of networks” to address fresh challenges as they are identified. In this Special Issue of Frontiers, diverse groups of environmental scientists discuss the current frontiers of research on continental change, focusing on North America. The framework for continental-scale science articulated by Peters et al. (p 229) brings together existing capacities, such as the National Science Foundation's Long Term Ecological Research network (http://lternet.edu), networks maintained by mission agencies of many countries, including Mexico's Commission for Knowledge and Use of Biodiversity (www.conabio.gob.mx), the Sub-global Assessments of the Millennium Ecosystem Assessment, international research networks such as the Global Lake Ecological Observatory Network (GLEON; http://gleon.org), and new networks currently under development, such as the National Ecological Observatory Network (NEON; www.neoninc.org). Other papers in this issue describe insights and opportunities for network research. Freshwater ecosystems serve as sentinels for their airsheds and watersheds, providing a natural matrix for continental sensor networks (Williamson et al., p 247). Contrasting ecosystem responses across gradients of urban impact and climate change reveal the effects of major human drivers (Grimm et al., p 264). Invasive species and emergent diseases can be strong drivers of greenlash, due to their capacity for contagious spread across landscapes (Crowl et al., p 238). Coastal ecosystems face some unique stressors, such as rising sea level and intensification of windstorms, suggesting important hypotheses to be tested across networked coastal sites (Hopkinson et al., p 255). In this century, climate change is the overarching environmental shift, establishing the context in which other drivers will act (Marshall et al., p 273). Networks of long-term observation sites are crucial for understanding how multiple drivers, acting across gradients of climate, land use, and ecosystem type, are changing the ecosystem services that support human well-being. Interdisciplinary assessments to synthesize data in policy-relevant form place increasing demands on the environmental sciences. Yet a recent evaluation of global ecosystems performed by the Millennium Ecosystem Assessment found that data were variable in quality. It was even more troubling that current data were sometimes inferior to historical information, so that recognition and understanding of ecosystem transformation was deteriorating even as change accelerated. In a world of greenlash, successful adaptation requires synoptic, continental-scale data on ecosystem change. The growing capacity of ecological networks is a remarkable step, addressing novel environmental challenges through self-organization of science. The site-specific depth and evolving connections of these networks do more than enable the frontier of environmental science – they are the frontier of environmental science. This Special Issue gives readers of Frontiers a bird's eye view of this rapidly developing area of inquiry.