Browsing by Subject "IMPACTS"

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Open Access
Assessing the effects of elephant foraging on the structure and diversity of an Afrotropical forest
(Biotropica, 2020-05-01) Rosin, Cooper; Beals, Kendall K; Belovitch, Michael W; Harrison, Ruby E; Pendred, Megan; Sullivan, Megan K; Yao, Nicolas; Poulsen, John R
African forest elephants (Loxodonta cyclotis) are ecosystem engineers that browse and damage large quantities of vegetation during their foraging and movement. Though elephant trail networks and clearings are conspicuous features of many African forests, the consequences of elephant foraging for forest structure and diversity are poorly documented. In this study in northeastern Gabon, we compare stem size, stem density, proportional damage, species diversity, and species relative abundance of seedlings and saplings in the vicinity of seven tree species that produce elephant-preferred fruits (“elephant trees”) relative to control trees that do not. Across 34 survey trees, with a combined census area of 2.04 ha, we recorded data on 26,128 woody stems in three sizes classes. Compared with control trees, the area around elephant trees had the following: (a) a significantly greater proportion of damaged seedlings and a marginally greater proportion of damaged saplings (with 82% and 24% greater odds of damage, respectively); (b) no significant difference in stem density or species diversity; and (c) a significantly greater relative abundance of seedlings of elephant tree species. Increasing distance away from focal elephant trees was associated with significantly reduced sapling stem damage, significantly increased sapling stem density, and significantly increased sapling species diversity. Considered in sum, our results suggest that elephants can affect the structure and diversity of Afrotropical forests through their foraging activities, with some variation based on location and plant size class. Developing a more complete understanding of elephants’ ecological effects will require continued research, ideally with manipulative experiments. Abstract in French is available with online material.
Open Access
Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: An expert assessment
(Environmental Research Letters, 2016-03-07) Abbott, BW; Jones, JB; Schuur, EAG; Chapin, FS; Bowden, WB; Bret-Harte, MS; Epstein, HE; Flannigan, MD; Harms, TK; Hollingsworth, TN; Mack, MC; McGuire, AD; Natali, SM; Rocha, AV; Tank, SE; Turetsky, MR; Vonk, JE; Wickland, KP; Aiken, GR; Alexander, HD; Amon, RMW; Benscoter, BW; Bergeron, Y; Bishop, K; Blarquez, O; Bond-Lamberty, B; Breen, AL; Buffam, I; Cai, Y; Carcaillet, C; Carey, SK; Chen, JM; Chen, HYH; Christensen, TR; Cooper, LW; Cornelissen, JHC; De Groot, WJ; Deluca, TH; Dorrepaal, E; Fetcher, N; Finlay, JC; Forbes, BC; French, NHF; Gauthier, S; Girardin, MP; Goetz, SJ; Goldammer, JG; Gough, L; Grogan, P; Guo, L; Higuera, PE; Hinzman, L; Hu, FS; Hugelius, G; Jafarov, EE; Jandt, R; Johnstone, JF; Karlsson, J; Kasischke, ES; Kattner, G; Kelly, R; Keuper, F; Kling, GW; Kortelainen, P; Kouki, J; Kuhry, P; Laudon, H; Laurion, I; MacDonald, RW; Mann, PJ; Martikainen, PJ; McClelland, JW; Molau, U; Oberbauer, SF; Olefeldt, D; Paré, D; Parisien, MA; Payette, S; Peng, C; Pokrovsky, OS; Rastetter, EB; Raymond, PA; Raynolds, MK; Rein, G; Reynolds, JF; Robards, M; Rogers, BM; Schdel, C; Schaefer, K; Schmidt, IK; Shvidenko, A; Sky, J; Spencer, RGM; Starr, G; Striegl, RG; Teisserenc, R; Tranvik, LJ; Virtanen, T; Welker, JM; Zimov, S
As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
Open Access
Climate change challenges the current conservation strategy for the giant panda
(Biological Conservation, 2015-10-01) Shen, Guozhen; Pimm, Stuart L; Feng, Chaoyang; Ren, Guofang; Liu, Yanping; Xu, Wenting; Li, Junqing; Si, Xingfeng; Xie, Zongqiang
The global total of protected areas to conserve biodiversity is increasing steadily, while numerous studies show that they are broadly effective. That said, how will current conservation strategies work, given the current and expected changes to the global climate? The giant panda is a conservation icon and exceptional efforts protect its remaining habitats. It provides a unique case study to address this question. There are many studies on the projected loss of habitats as climate warms, but few consider the geographical arrangement of future habitats, current protected area, and species' dispersal abilities. Most alarmingly, we expect much greater habitat fragmentation after climate change. Here, we combine long-term data on giant pandas with climate-change scenarios to predict future habitat loss and distribution in the Min Shan of Sichuan and Gansu, China. We employ metapopulation capacity as a mechanistic measure of a species' response to habitat fragmentation. The results show that climate changes will lead to 16.3. ±. 1.4 (%) losses of giant panda habitats. Alarmingly, 11.4% of the remaining habitat fragments would be smaller than the extinction threshold area as the extent of fragmentation increases nearly fourfold. The projected fragmentation of giant panda habitats predicts 9% lower effectiveness inside the protected area network compared with that outside of reserves. A 35% reduction will occur in future effectiveness of reserve networks. The results challenge the long-term effectiveness of protected areas in protecting the species' persistence. They indicate a need for integrating both natural processes and dynamic threats over a simple reliance on individual static natural reserves.
Open Access
Conceptualizing and operationalizing human wellbeing for ecosystem assessment and management
(Environmental Science and Policy, 2016-12-01) Breslow, SJ; Sojka, B; Barnea, R; Basurto, X; Carothers, C; Charnley, S; Coulthard, S; Dolšak, N; Donatuto, J; García-Quijano, C; Hicks, CC; Levine, A; Mascia, MB; Norman, K; Poe, M; Satterfield, T; Martin, KS; Levin, PS
© 2016 Elsevier Ltd There is growing interest in assessing the effects of changing environmental conditions and management actions on human wellbeing. A challenge is to translate social science expertise regarding these relationships into terms usable by environmental scientists, policymakers, and managers. Here, we present a comprehensive, structured, and transparent conceptual framework of human wellbeing designed to guide the development of indicators and a complementary social science research agenda for ecosystem-based management. Our framework grew out of an effort to develop social indicators for an integrated ecosystem assessment (IEA) of the California Current large marine ecosystem. Drawing from scholarship in international development, anthropology, geography, and political science, we define human wellbeing as a state of being with others and the environment, which arises when human needs are met, when individuals and communities can act meaningfully to pursue their goals, and when individuals and communities enjoy a satisfactory quality of life. We propose four major social science-based constituents of wellbeing: connections, capabilities, conditions, and cross-cutting domains. The latter includes the domains of equity and justice, security, resilience, and sustainability, which may be assessed through cross-cutting analyses of other constituents. We outline a process for identifying policy-relevant attributes of wellbeing that can guide ecosystem assessments. To operationalize the framework, we provide a detailed table of attributes and a large database of available indicators, which may be used to develop measures suited to a variety of management needs and social goals. Finally, we discuss four guidelines for operationalizing human wellbeing measures in ecosystem assessments, including considerations for context, feasibility, indicators and research, and social difference. Developed for the U.S. west coast, the framework may be adapted for other regions, management needs, and scales with appropriate modifications.
Open Access
Free-ranging livestock threaten the long-term survival of giant pandas
(Biological Conservation, 2017-12-01) Li, Binbin V; Pimm, Stuart L; Li, Sheng; Zhao, Lianjun; Luo, Chunping
© 2017 Elsevier Ltd China has implemented forest policies and expanded protected areas to halt deforestation and protect giant panda habitats. These policies simultaneously encouraged local communities to raise livestock that then freely range in forests. This grazing had unintended consequences. As an alternative livelihood, it has become the most prevalent human disturbance across the panda's range. How do free-ranging livestock impact giant panda habitats and what are the implications for future conservation and policy on a larger scale? We use Wanglang National Nature Reserve as a case study. It has seen a nine-fold livestock increase during past 15 years. We combined bamboo survey plots, GPS collar tracking, long-term monitoring, and species distribution modelling incorporating species interaction to understand the impacts across spatial and temporal scales. Our results showed that livestock, especially horses, lead to a significant reduction of bamboo biomass and regeneration. The most intensively used areas by livestock are in the valleys, which are also the areas that pandas prefer. Adding livestock presence to predictive models of the giant panda's distribution yielded a higher accuracy and suggested livestock reduce panda habitat by 34%. Pandas were driven out of the areas intensively used by livestock. We recommend the nature reserve carefully implement a livestock ban and prioritise removing horses because they cause the greater harm. To give up livestock, local communities prefer long-term subsidies or jobs to a one-time payment. Thus, we recommend the government provide payments for ecosystem services that create jobs in forest stewardship or tourism while reducing the number of domestic animals.
Open Access
Seabird trophic position across three ocean regions tracks ecosystem differences
(Frontiers in Marine Science, 2018-09-07) Gagné, TO; Hyrenbach, KD; Hagemann, ME; Bass, OL; Pimm, SL; MacDonald, M; Peck, B; Van Houtan, KS
We analyze recently collected feather tissues from two species of seabirds, the sooty tern (Onychoprion fuscatus) and brown noddy (Anous stolidus), in three ocean regions (North Atlantic, North Pacific, and South Pacific) with different human impacts. The species are similar morphologically and in the trophic levels from which they feed within each location. In contrast, we detect reliable differences in trophic position amongst the regions. Trophic position appears to decline as the intensity of commercial fishing increases, and is at its lowest in the Caribbean. The spatial gradient in trophic position we document in these regions exceeds those detected over specimens from the last 130 years in the Hawaiian Islands. Modeling suggests that climate velocity and human impacts on fish populations strongly align with these differences.