When scientists publish an analysis of the impacts of climate change on species, ecosystems and people, the language used can sound terribly distant and cold. In truth, the tone of these studies reflects the tone of science but not the feelings of scientists.
Ecologists studying the impacts of climate change today know that change is not coming at some point in the future; change is here, with much more to come. And most of us are pretty worried -- a heat reflected even in the cool questions we as scientists are now asking.
In this post, I highlight findings drawn from recent science published by the Open Access publisher, PLOS (Public Library of Science), titled The 2014 Ecological Impacts of Climate Change Collection, 18 studies published in PLOS Biology and PLOS ONE over the past year, covering everything from the effects of global warming and other climate-related changes on penguin, frog, butterfly and human communities to proposed models for deciding which species might be moved to improve their chances for survival. These papers were chosen by PLOS ONE Section Editor Ben Bond-Lamberty, an ecologist whose research focuses on carbon cycling in terrestrial ecosystems, to coincide with the 99th annual meeting of the 10,000 member Ecological Society of America (ESA), August 10-15 in Sacramento. Relevant beyond the walls of ESA, these PLOS climate change publications reflect the emerging complexity of the science and the greater urgency felt by scientists doing the research.
Photo by John A. Kelley, USDA Natural Resources Conservation Service
Atmospheric science for the current period of global warming dates back only to the mid-1960s or early 1970s, though a 19-century chemist first postulated a mechanism between burning coal and climate change.
In contrast, the ecological science of climate change impacts is more recent, dating back only to the mid-1990s, when substantive papers by the likes of Camille Parmesan and Terry Root showed some of the first credible evidence of 20th-century range shifts in wild species.
A First Generation Sounds the Alarm
The first generation of ecological research exploring 20th-century warming primarily focused on species and population levels. Research eventually expanded to historical trend analyses of climate linkages by well-documented (often domesticated) populations and species as well as phenological studies (shifts in the timing of behaviors such as migration or flowering dates). More recently, there has been a proliferation of work focused specifically on how to untangle impacts that may occur in coming decades. These usually combine assumptions about "climate envelopes" or ranges of suitable conditions for species survival, ecophysiology (the adaptation of an organism's physiology to environmental conditions) and applications of climate model projections of temperature and precipitation to those envelopes.
This first 10 or 12 years of ecological research told some important stories but often lacked nuance or complexity. Embedded within many of these first-generation papers is a sense that we more or less know what kinds of climate trends are emerging, and we also more or less know what kinds of ecological impacts will occur. Climate change was often viewed as an isolated, simple, and knowable driver. If we can infer the sensibility of the authors of this period, it would be that risks to species and ecosystems are increasing -- and somebody needs to do something.
"Solutions" to climate change were largely envisioned as challenges beyond the purview of science, often limited to reducing or eliminating greenhouse gas emissions.
The Second Generation Emerges: Better Questions, Actionable Answers
I would argue that beginning about 2010, we entered the second generation of climate impacts ecology, with a marked growth in maturity and sophistication. Studies have explored multivariate impacts on ecological communities, species with limited historical or monitoring records, experimental and comparative studies, robust linkages with biophysical processes and the implications of resource management and economic development decisions. In this body of work, I have been struck by how climate change studies are becoming normalized and mainstreamed within ecology rather than remaining isolated.
Perhaps the emerging message coming from this shift in science is that we need to know definitively why patterns are emerging, and we -- the environmental science community -- need to come up with some effective responses. In other words, we need to do something.
Five trends stand out in papers contained in The PLOS 2014 Ecological Impacts of Climate Change Collection, as significant markers of progress towards solutions:
1. Ecological responses at population, species and community levels show patterns that are very difficult to predict and anticipate. In contrast to first generation papers, there is a growing recognition that not all species in an ecosystem, including closely related taxa or even all nearby populations within a single species, are responding to the same climate impacts in the same way, suggesting that predicting future climate responses by species is very difficult.
Ryan and colleagues show how tropical frogs exhibit a wide diversity of responses, while soil warming experiments by Anadon-Rosell and colleagues with alpine shrubs showed important variations in phenological triggers that are likely to result in important shifts in community composition. Pringle and colleagues demonstrate how shifts in water stress and herbivory patterns (both connected to weather events) can actually strengthen plant-insect mutualism, while Roth and colleagues found that altitudinal gradients remixed vertebrate, plant, and insect communities over time. Earlier papers often suggested that species, at least in the same genus or family or community, would respond to similar drivers and in similar patterns.
This assumption appears to have little evidence for support. Perhaps to paraphrase Tolstoy, all climate-perturbed populations are impacted in their own way.
2. Paleoecology can inform contemporary patterns. For instance, Feurdean and colleagues found that the recolonization of tree species following the end of the last glacial period was not simply a movement from south to north but a mosaic of migration, with patches of isolated tree communities left behind with the onset of glacial advances. They suggest that microclimates, microrefugia and the translocation of many species by humans outside of their natural range will play an important role in range shifts in the future. Paleoecology as a subdiscipline is an increasingly significant reservoir of data and analogs for understanding range shifts, disturbance regime variability, and community reassembly processes.
3. Ecosystem-level impacts are more than the accumulation of population responses. Tait and Schiel, for instance, showed that macroalgae assemblages showed more dramatic responses to elevated temperatures than as individual species, with the potential to alter NPP in coastal systems. In keeping with the first trend above, complex synergies and feedback systems are likely to be rippling through ecosystems in ways that are hard to both track and predict.
4. Climate change can accentuate impacts from societal shifts.
Riordan and Rundel, for instance, point to the potential for increasing competition between human and natural systems in California, as species and key social and economic activities track local climate patterns -- creating yet more California real estate problems.
Kaniewski and colleagues showed evidence over a 4000-year period that coastal Mediterranean ecosystems have responded to shifts in urbanization, sea-level rise, climate variability, and resource use in a paper that bridges archaeology, climate science, and both terrestrial and marine ecology. A key implication in both papers is that climate change's interactions with broader environmental change will not be linear.
Image: Melitaea trivia syriaca 1CC BY 3.0 Gideon Pisanty (Gidip) גדעון פיזנטי -
5. Existing conservation and sustainable resource management approaches will require rethinking in many regions. Zografou and colleagues point to one of the cornerstones of conservation -- fixed-boundary protected areas -- and suggest that rapid shifts in butterfly community composition associated with climate change are eroding the ability to conserve these species. Amorim and colleagues point to efforts to track range shifts that may be occurring in Iberian bat species -- will we have the monitoring networks in the right places to detect changes in progress.
Critically, Rout and colleagues suggested a systematic and quantifiable decision-making approach to decide if and when we should move species to new areas. In all of these cases, the evidence base for climate-informed resource management appears to be small so far.
Outlines for the Future: Better Science, Better Action?
One of the significant risks in our time is that policy and resource management decisions get too far ahead of what science can usefully inform. Unfortunately, science can lag the pace that decision makers need. The answer to my initial question -- do we know where we're going? -- has two parts: do we know where ecosystems and the climate are going, and do we know the voice that ecology as a discipline can articulate in making better decisions?
Ecologists have arguably lagged behind our evolutionary biologist cousins in moving from weather-based analyses to climate-based thinking, with the notable exception of paleoecology. But we are catching up fast. As a science, ecology is the major scientific source that underlies how we define conservation. While not all of ecology is not relevant or applied to conservation, ecology is arguably the most important discipline for conservation science, sustainable resource management, and -- even more broadly -- sustainability itself.
The cool language of science doesn't capture the passion driving research into global warming: What is happening to ecosystems and ecological processes? What can we expect and reasonably predict will be happen? What will these changes mean to our livelihoods and economies? Do we know enough about where we are going to ease the transition for ourselves and the species and ecosystems we care about?
These papers suggest that confident predictions about future trends may be slow in coming -- or may never come. And as a result, we may need to rethink what we are managing, protecting, and conserving. Ultimately, these papers may be collectively pointing to a larger transition within ecology itself from a science of "conservation" -- managing to restore or to reduce, minimize, or reverse change -- and moving towards a science that can enable ecological integrity as populations, communities, ecosystems, and economies reorganize themselves in the face of inevitable change.