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Attributing physical and biological impacts to anthropogenic climate change
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Significant changes in physical and biological systems are occurring on all continents and in most oceans, with a concentration of available data in Europe and North America. Most of these changes are in the direction expected with warming temperature. Here we show that these changes in natural systems since at least 1970 are occurring in regions of observed temperature increases, and that these temperature increases at continental scales cannot be explained by natural climate variations alone. Given the conclusions from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report that most of the observed increase in global average temperatures since the mid-twentieth century is very likely to be due to the observed increase in anthropogenic greenhouse gas concentrations, and furthermore that it is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica, we conclude that anthropogenic climate change is having a significant impact on physical and biological systems globally and in some continents.
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Biodiversity and ecosystem multifunctionality
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Biodiversity loss can affect ecosystem functions and services1–4. Individual ecosystem functions generally show a positive asymptotic relationship with increasing biodiversity, suggesting that some species are redundant5–8. However, ecosystems are managed and conserved for multiple functions, which may require greater biodiversity. Here we present an analysis of published data from grassland biodiversity experiments9–11, and show that ecosystem multifunctionality does require greater numbers of species. We analysed each ecosystem function alone to identify species with desirable effects. We then calculated the number of species with positive effects for all possible combinations of functions. Our results show appreciable differences in the sets of species influ- encing different ecosystem functions, with average proportional overlap of about 0.2 to 0.5. Consequently, as more ecosystem pro- cesses were included in our analysis, more species were found to affect overall functioning. Specifically, for all of the analysed experiments, there was a positive saturating relationship between the number of ecosystem processes considered and the number of species influencing overall functioning. We conclude that because different species often influence different functions, studies focus- ing on individual processes in isolation will underestimate levels of biodiversity required to maintain multifunctional ecosystems.
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Conservation value of forests attacked by bark beetles: Highest number of indicator species is found in early successional stages
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Heavy natural disturbance in large protected areas of former commercial forests increasingly evokes European parliaments to call for management intervention because a loss of habitats and species is feared. In contrast, natural early successional habitats have recently been recognised as important for conservation. Current knowledge in this field mostly results from studies dealing only with selected taxa. Here we analyse the success of species across 24 lineages of three kingdoms in the Bavarian Forest National Park (Germany) after 15 years of a European spruce bark beetle (Ips typographus L.) outbreak that led to rapid canopy opening. Using indicator species analysis, we found 257 species with a significant preference for open forests and 149 species with a preference for closed forests, but only 82 species with a preference for the stand conditions transitional between open and closed forests. The large number of species with a preference for open forests across lineages supports the role of this bark beetle as a keystone species for a broad array of species. The slowdown of the outbreak after 15 years in the core zone of the national park resulted in less than half of the area being affected, due to variability in stand ages and tree species mixtures. Our case study is representative of the tree species composition and size of many large protected montane areas in Central European countries and illustrates that (1) natural disturbances increase biodiversity in formerly managed forests and (2) a montane protected area spanning 10,000 ha of low range mountains is likely sufficient to allow natural disturbances without a biased loss of closed-forest species.
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BOTANY AND A CHANGING WORLD: INTRODUCTION TO THE SPECIAL ISSUE ON GLOBAL BIOLOGICAL CHANGE
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The impacts of global change have heightened the need to understand how organisms respond to and influence these changes. Can we forecast how change at the global scale may lead to biological change? Can we identify systems, processes, and organisms that are most vulnerable to global changes? Can we use this understanding to enhance resilience to global changes? This special issue on global biological change emphasizes the integration of botanical information at different biological levels to gain perspective on the direct and indirect effects of global change. Contributions span a range of spatial scales and include both ecological and evolutionary timescales and highlight work across levels of organization, including cellular and physiological processes, individuals, populations, and ecosystems. Integrative botanical approaches to global change are critical for the eco- logical and evolutionary insights they provide and for the implications these studies have for species conservation and ecosys- tem management.
Key words: community dynamics; flowering phenology; functional traits; global biological change; invasive species; land-use patterns; plant–microbial interactions; species interactions.
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Ecological Effects of Prescribed Fire Season: A Literature Review and Synthesis for Managers
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Prescribed burning may be conducted at times of the year when fires were infrequent historically, leading to concerns about potential adverse effects on vegetation and wildlife. Historical and prescribed fire regimes for different regions in the continental United States were compared and literature on season of prescribed burning synthesized. In regions and vegetation types where considerable differences in fuel consumption exist among burning seasons, the effects of prescribed fire season appears, for many ecological variables, to be driven more by fire-intensity differences among seasons than by phenology or growth stage of organisms at the time of fire. Where fuel consumption differs little among burning seasons, the effect of phenology or growth stage of organisms is often more apparent, presumably because it is not overwhelmed by fire-intensity differences. Most species in ecosystems that evolved with fire appear to be resilient to one or few out-of-season prescribed burn(s). However, a variable fire regime including prescribed burns at different times of the year may alleviate the potential for undesired changes and maximize biodiversity.
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Ecological extinction and evolution in the brave new ocean
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The great mass extinctions of the fossil record were a major creative force that provided entirely new kinds of opportunities for the subsequent explosive evolution and diversification of surviving clades. Today, the synergistic effects of human impacts are laying the groundwork for a comparably great Anthropocene mass extinction in the oceans with unknown ecological and evolutionary consequences. Synergistic effects of habitat destruction, overfishing, introduced species, warming, acidification, toxins, and massive runoff of nutrients are transforming once complex ecosystems like coral reefs and kelp forests into monotonous level bottoms, transforming clear and productive coastal seas into anoxic dead zones, and transforming complex food webs topped by big animals into simplified, microbially dominated ecosystems with boom and bust cycles of toxic dinoflagel- late blooms, jellyfish, and disease. Rates of change are increasingly fast and nonlinear with sudden phase shifts to novel alternative community states. We can only guess at the kinds of organisms that will benefit from this mayhem that is radically altering the selective seascape far beyond the consequences of fishing or warming alone. The prospects are especially bleak for animals and plants compared with metabolically flexible microbes and algae. Halting and ultimately reversing these trends will require rapid and fundamental changes in fisheries, agricultural practice, and the emissions of green- house gases on a global scale.
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Biodiversity management in the face of climate change: A review of 22 years of recommendations
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Climate change creates new challenges for biodiversity conservation. Species ranges and ecological dynamics are already responding to recent climate shifts, and current reserves will not continue to support all species they were designed to protect. These problems are exacerbated by other global changes. Scholarly articles recommending measures to adapt conservation to climate change have proliferated over the last 22 years. We systematically reviewed this literature to explore what potential solutions it has identified and what consensus and direction it provides to cope with climate change. Several consistent recommendations emerge for action at diverse spatial scales, requiring leadership by diverse actors. Broadly, adaptation requires improved regional institutional coordination, expanded spatial and temporal perspective, incorporation of climate change scenarios into all planning and action, and greater effort to address multiple threats and global change drivers simultaneously in ways that are responsive to and inclusive of human communities. However, in the case of many recommendations the how, by whom, and under what conditions they can be implemented is not specified. We synthesize recommendations with respect to three likely conservation pathways: regional planning; site-scale management; and modification of existing conservation plans. We identify major gaps, including the need for (1) more specific, operational examples of adaptation principles that are consistent with unavoidable uncertainty about the future; (2) a practical adaptation planning process to guide selection and integration of recommendations into existing policies and programs; and (3) greater integration of social science into an endeavor that, although dominated by ecology, increasingly recommends extension beyond reserves and into human-occupied landscapes.
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Assessing potential climate change effects on vegetation using a linked model approach
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We developed a process that links the mechanistic power of dynamic global vegetation models with the detailed vegetation dynamics of state-and-transition models to project local vegetation shifts driven by projected climate change. We applied our approach to central Oregon (USA) ecosystems using three climate change scenarios to assess potential future changes in species composition and community structure. Our results suggest that: (1) legacy effects incorporated in state-and-transition models realistically dampen climate change effects on vegetation; (2) species-specific response to fire built into state-and- transition models can result in increased resistance to climate change, as was the case for ponderosa pine (Pinus ponderosa) forests, or increased sensitivity to climate change, as was the case for some shrublands and grasslands in the study area; and (3) vegetation could remain relatively stable in the short term, then shift rapidly as a consequence of increased disturbance such as wildfire and altered environmental conditions. Managers and other land stewards can use results from our linked models to better anticipate potential climate-induced shifts in local vegetation and resulting effects on wildlife habitat.
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Classification of Climate Change-Induced Stresses on Biological Diversity
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Conservation actions need to account for and be adapted to address changes that will occur under global climate change. The identification of stresses on biological diversity (as defined in the Convention on Biological Diversity) is key in the process of adaptive conservation management. We considered any impact of climate change on biological diversity a stress because such an effect represents a change (negative or positive) in key ecological attributes of an ecosystem or parts of it. We applied a systemic approach and a hierarchical framework in a comprehensive classification of stresses to biological diversity that are caused directly by global climate change. Through analyses of 20 conservation sites in 7 countries and a review of the literature, we identified climate-change-induced stresses. We grouped the identified stresses according to 3 levels of biological diversity: stresses that affect individuals and populations, stresses that affect biological communities, and stresses that affect ecosystem structure and function. For each stress category, we differentiated 3 hierarchical levels of stress: stress class (thematic grouping with the coarsest resolution, 8); general stresses (thematic groups of specific stresses, 21); and specific stresses (most detailed definition of stresses, 90). We also compiled an overview of effects of climate change on ecosystem services using the categories of the Millennium Ecosystem Assessment and 2 additional categories. Our classification may be used to identify key climate-change-related stresses to biological diversity and may assist in the development of appropriate conservation strategies. The classification is in list format, but it accounts for relations among climate-change-induced stresses.
Keywords: adaptation, conservation, strategies,adaptive management,climatechange,conservation planning, conservation targets, hierarchical framework, threats to biological diversity
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Biodiversity effects on ecosystem functioning change along environmental stress gradients
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Positive relationship between biodiversity and ecosystem functioning has been observed in many studies, but how this relationship is affected by environmental stress is largely unknown. To explore this influence, we measured the biomass of microalgae grown in microcosms along two stress gradients, heat and salinity, and compared our results with 13 published case studies that measured biodiversity–ecosystem functioning relationships under varying environmental conditions. We found that positive effects of biodiversity on ecosystem functioning decreased with increasing stress intensity in absolute terms. However, in relative terms, increasing stress had a stronger negative effect on low-diversity communities. This shows that more diverse biotic communities are functionally less susceptible to environmental stress, emphasises the need to maintain high levels of biodiversity as an insurance against impacts of changing environmental conditions and sets the stage for exploring the mechanisms underlying biodiversity effects in stressed ecosystems.
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