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Livelihood resilience in the face of climate change
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The resilience concept requires greater attention to human livelihoods if it is to address the limits to adaptation strategies and the development needs of the planet’s poorest and most vulnerable people. Although the concept of resilience is increasingly informing research and policy, its transfer from ecological theory to social systems leads to weak engagement with normative, social and political dimensions of climate change adaptation. A livelihood perspective helps to strengthen resilience thinking by placing greater emphasis on human needs and their agency, empowerment and human rights, and considering adaptive livelihood systems in the context of wider transformational changes.
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Global protected area expansion is compromised by projected land-use and parochialism
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Protected areas are one of the main tools for halting the continuing global biodiversity crisis1–4 caused by habitat loss, fragmentation and other anthropogenic pressures5–8. According to the Aichi Biodiversity Target 11 adopted by the Convention on Biological Diversity, the protected area network should be expanded to at least 17% of the terrestrial world by 2020 (http://www.cbd.int/sp/targets). To max- imize conservation outcomes, it is crucial to identify the best expan- sion areas. Here we show that there is a very high potential to increase protection of ecoregions and vertebrate species by expanding the pro- tected area network, but also identify considerable risk of ineffective outcomes due to land-use change and uncoordinated actions between countries. We use distribution data for 24,757 terrestrial vertebrates assessed under the International Union for the Conservation of Nature (IUCN) ‘red list of threatened species’9, and terrestrial eco- regions10 (827), modified by land-use models for the present and 2040, and introduce techniques for global and balanced spatial con- servation prioritization. First, we show that with a coordinated global protected area network expansion to 17% of terrestrial land, average protection of species ranges and ecoregions could triple. Second, if projected land-use change by 2040 (ref. 11) takes place, it becomes infeasible to reach the currently possible protection levels, and over 1,000 threatened species would lose more than 50% of their present effective ranges worldwide. Third, we demonstrate a major efficiency gap between national and global conservation priorities. Strong evi- dence is shown that further biodiversity loss is unavoidable unless international action is quickly taken to balance land-use and biodiversity conservation. The approach used here can serve as a framework for repeatable and quantitative assessment of efficiency, gaps and expansion of the global protected area network globally, regionally and nationally, considering current and projected land-use pressures.
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Critical slowing down as early warning for the onset of collapse in mutualistic communities
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Tipping points are crossed when small changes in external conditions cause abrupt unexpected responses in the current state of a system. In the case of ecological communities under stress, the risk of approaching a tipping point is unknown, but its stakes are high. Here, we test recently developed critical slowing-down indicators as early-warning signals for detecting the proximity to a potential tipping point in structurally complex ecological communities. We use the structure of 79 empirical mutualistic networks to simulate a scenario of gradual environmental change that leads to an abrupt first extinction event followed by a sequence of species losses until the point of complete community collapse. We find that critical slowing-down indicators derived from time series of bio- masses measured at the species and community level signal the proximity to the onset of community collapse. In particular, we identify specialist species as likely the best-indicator species for mon- itoring the proximity of a community to collapse. In addition, trends in slowing-down indicators are strongly correlated to the timing of species extinctions. This correlation offers a promising way for map- ping species resilience and ranking species risk to extinction in a given community. Our findings pave the road for combining theory on tipping points with patterns of network structure that might prove useful for the management of a broad class of ecological networks under global environmental change.
resilience | critical transition | mutualism | ecological networks | pollinator decline
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Rapid deposition of oxidized biogenic compounds to a temperate forest
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We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H2O2), nitric acid (HNO3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, satu- rated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO3 making up the balance. We ob- serve that water-soluble compounds (e.g., strong acids and hydro- peroxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbon- yls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffu- sivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (∼1 nmol m−2·s−1). GEOS−Chem, a widely used atmospheric chemical transport model, currently under- estimates dry deposition for most molecules studied in this work. Reconciling GEOS−Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface con- centration of trace gases.
biosphere−atmosphere exchange | isoprene | dry deposition | OVOCs | fluxes
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Recovery of large carnivores in Europe’s modern human-dominated landscapes
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The conservation of large carnivores is a formidable challenge for biodiversity conservation. Using a data set on the past and current status of brown bears (Ursus arctos), Eurasian lynx (Lynx lynx), gray wolves (Canis lupus), and wolverines (Gulo gulo) in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible. The European situation reveals that large carnivores and people can share the same landscape.
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Temporal stability in forest productivity increases with tree diversity due to asynchrony in species dynamics
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Theory predicts a positive relationship between biodiversity and stability in ecosystem properties, while diversity is expected to have a negative impact on stability at the species level. We used virtual experiments based on a dynamic simulation model to test for the diversity–stability relationship and its underlying mechanisms in Central European forests. First our results show that variability in productivity between stands differing in species composition decreases as species richness and functional diversity increase. Second we show temporal stability increases with increasing diversity due to compensatory dynamics across species, supporting the biodiversity insurance hypothesis. We demonstrate that this pattern is mainly driven by the asynchrony of spe- cies responses to small disturbances rather than to environmental fluctuations, and is only weakly affected by the net biodiversity effect on productivity. Furthermore, our results suggest that com- pensatory dynamics between species may enhance ecosystem stability through an optimisation of canopy occupancy by coexisting species.
Keywords
Asynchrony, biodiversity, ecosystem functioning, ecosystem predictability, forests, gap model, insurance hypothesis, productivity, stability, structural equation model.
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Controls on Annual Forest Carbon Storage: Lessons from the Past and Predictions for the Future
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The temperate forests of North America may play an important role in future carbon (C) sequestration strategies. New, multiyear, ecosystem-scale C cycling studies are providing a process-level understanding of the factors controlling annual forest C storage. Using a combination of ecological and meteorological methods, we quantified the response of annual C storage to historically widespread disturbances, forest succession, and climate variation in a common forest type of the upper Great Lakes region. At our study site in Michigan, repeated clear-cut harvesting and fire disturbance resulted in a lasting decrease in annual forest C storage. However, climate variation exerts a strong control on C storage as well, and future climate change may substantially reduce annual C storage by these forests. Annual C storage varies through ecological succession by rising to a maximum and then slowly declining in old-growth stands. Effective forest C sequestration requires the management of all C pools, including traditionally managed pools such as bole wood and also harvest residues and soils.
Keywords: forests, carbon, climate change, succession, disturbance
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Conservation threats: biofuel
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Biofuels: Europe’s largest conservation charity has launched a campaign to heighten the threat to wildlife habitats and biodiversity from plantations of fuel crops. Nigel Williams reports. 1st paragraph: Europe embraced the theoretical potential that biofuels might offer both in terms of climate change and renewable sources of energy, as enthusiastically as anywhere else, but the dawning reality has hit harder here than in many other areas with the realisation that it is a crowded continent with limited scope for home-grown material.
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Impacts of plant diversity on biomass production increase through time because of species complementarity
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We summarize the results of 44 experiments that have manipulated the richness of plants to examine how plant diversity affects the production of biomass. We show that mixtures of species produce an average of 1.7 times more biomass than species monocultures and are more productive than the average monocul- ture in 79% of all experiments. However, in only 12% of all experiments do diverse polycultures achieve greater biomass than their single most productive species. Previously, a positive net effect of diversity that is no greater than the most productive species has been interpreted as evidence for selection effects, which occur when diversity maximizes the chance that highly productive species will be included in and ultimately dominate the biomass of polycultures. Contrary to this, we show that although productive species do indeed contribute to diversity effects, these contributions are equaled or exceeded by species complementar- ity, where biomass is augmented by biological processes that involve multiple species. Importantly, both the net effect of diver- sity and the probability of polycultures being more productive than their most productive species increases through time, because the magnitude of complementarity increases as experiments are run longer. Our results suggest that experiments to date have, if anything, underestimated the impacts of species extinction on the productivity of ecosystems.
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Forest fuel reduction alters fire severity and long-term carbon storage in three Pacific Northwest ecosystems
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Abstract. Two forest management objectives being debated in the context of federally managed landscapes in the U.S. Pacific Northwest involve a perceived trade-off between fire restoration and carbon sequestration. The former strategy would reduce fuel (and therefore C) that has accumulated through a century of fire suppression and exclusion which has led to extreme fire risk in some areas. The latter strategy would manage forests for enhanced C sequestration as a method of reducing atmospheric CO2 and associated threats from global climate change. We explored the trade-off between these two strategies by employing a forest ecosystem simulation model, STANDCARB, to examine the effects of fuel reduction on fire severity and the resulting long-term C dynamics among three Pacific Northwest ecosystems: the east Cascades ponderosa pine forests, the west Cascades western hemlock–Douglas-fir forests, and the Coast Range western hemlock–Sitka spruce forests. Our simulations indicate that fuel reduction treatments in these ecosystems consistently reduced fire severity. However, reducing the fraction by which C is lost in a wildfire requires the removal of a much greater amount of C, since most of the C stored in forest biomass (stem wood, branches, coarse woody debris) remains unconsumed even by high-severity wildfires. For this reason, all of the fuel reduction treatments simulated for the west Cascades and Coast Range ecosystems as well as most of the treatments simulated for the east Cascades resulted in a reduced mean stand C storage. One suggested method of compensating for such losses in C storage is to utilize C harvested in fuel reduction treatments as biofuels. Our analysis indicates that this will not be an effective strategy in the west Cascades and Coast Range over the next 100 years. We suggest that forest management plans aimed solely at ameliorating increases in atmospheric CO2 should forgo fuel reduction treatments in these ecosystems, with the possible exception of some east Cascades ponderosa pine stands with uncharacteristic levels of understory fuel accumulation. Balancing a demand for maximal landscape C storage with the demand for reduced wildfire severity will likely require treatments to be applied strategically throughout the landscape rather than indiscriminately treating all stands.
Key words: biofuels; carbon sequestration; fire ecology; fuel reduction treatment; Pacific Northwest, USA; Picea sitchensis; Pinus ponderosa; Pseudotsuga menziesii.
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