Showing papers by "Guy F. Midgley published in 2007"

Protected area needs in a changing climate

Abstract: Range shifts due to climate change may cause species to move out of protected areas. Climate change could therefore result in species range dynamics that reduce the relevance of current fixed protected areas in future conservation strategies. Here, we apply species distribution modeling and conservation planning tools in three regions (Mexico, the Cape Floristic Region of South Africa, and Western Europe) to examine the need for additional protected areas in light of anticipated species range shifts caused by climate change. We set species representation targets and assessed the area required to meet those targets in the present and in the future, under a moderate climate change scenario. Our findings indicate that protected areas can be an important conservation strategy in such a scenario, and that early action may be both more effective and less costly than inaction or delayed action. According to our projections, costs may vary among regions and none of the three areas studied will fully meet all conservation targets, even under a moderate climate change scenario. This suggests that limiting climate change is an essential complement to adding protected areas for conservation of biodiversity.

A changing climate is eroding the geographical range of the Namib Desert tree Aloe through population declines and dispersal lags

Abstract: While poleward species migration in response to recent climatic warming is widely documented, few studies have examined entire range responses of broadly distributed sessile organisms, including changes on both the trailing (equatorward) and the leading (poleward) range edges. From a detailed population census throughout the entire geographical range of Aloe dichotoma Masson, a long-lived Namib Desert tree, together with data from repeat photographs, we present strong evidence that a developing range shift in this species is a ‘fingerprint’ of anthropogenic climate change. This is explained at a high level of statistical significance by population level impacts of observed regional warming and resulting water balance constraints. Generalized linear models suggest that greater mortalities and population declines in equatorward populations are virtually certainly the result, due to anthropogenic climate change, of the progressive exceedance of critical climate thresholds that are relatively closer to the species’ tolerance limits in equatorward sites. Equatorward population declines are also broadly consistent with bioclimatically modelled projections under anticipated anthropogenic climate change but, as yet, there is no evidence of poleward range expansion into the area predicted to become suitable in future, despite good evidence for positive population growth trends in poleward populations. This study is among the first to show a marked lag between trailing edge population extinction and leading edge range expansion in a species experiencing anthropogenic climate change impacts, a pattern likely to apply to most sessile and poorly dispersed organisms. This provides support for conservative assumptions of species’ migration rates when modelling climate change impacts for such species. Aloe dichotoma ’s response to climate change suggests that desert ecosystems may be more sensitive to climate change than previously suspected.

Colonization and persistence ability explain the extent to which plant species fill their potential range

Abstract: Aim How species traits and environmental conditions affect biogeographical dynamics is poorly understood. Here we test whether estimates of a species’ evolutionary age, colonization and persistence ability can explain its current ‘range filling’ (the ratio between realized and potential range size). Location Fynbos biome (Cape Floristic Region, South Africa). Methods For 37 species of woody plants (Proteaceae), we estimate range filling using atlas data and distribution models, evolutionary age using molecular phylogenies, and persistence ability using estimates of individual longevity (which determines the probability of extinction of local populations). Colonization ability is estimated from validated process-based seed dispersal models, the arrangement of potential habitat, and data on local abundance. To relate interspecific variation in range filling to evolutionary age, colonization and persistence ability, we use two complementary model types: phenomenological linear models and the process-based metapopulation model of Levins. Results Linear model analyses show that range filling increases with a species’ colonization and persistence ability but is not affected by species age. Moreover, colonization ability is a better predictor of range filling than its component variables (local abundance and dispersal ability). The phylogenetically independent interaction between colonization and persistence ability is significant ( P < 0.05) for 97% of 180 alternative phylogenies. While the selected linear model explains 42% of the variance in arcsine transformed range filling, the Levins model performs more poorly. It overestimates range filling for realistic parameter values and produces unrealistic parameter estimates when fitted statistically. Main conclusions Colonization and local extinction seem to shape Proteaceae range dynamics on ecological rather than macroevolutionary time-scales. Our results suggest that the positive abundance‐range size relationship in this group is due primarily to the effect of abundance on colonization. In summary, this study contributes to a process-based understanding of range dynamics and highlights the importance of colonization for the future survival of Fynbos Proteaceae.

No forest left behind.

Abstract: New research indicates that slowing tropical deforestation may play a much larger role in mitigating climate change than previously believed [1,2]. Carbon emissions from tropical deforestation are expected to increase atmospheric CO2 concentration by between 29 and 129 ppm within 100 years, much more than previously estimated [3]. The parties to the United Nations Framework Convention on Climate Change are considering policy approaches and incentives for reducing emissions from deforestation (RED) in developing countries [4–6] that are timely, in light of these recent research findings. The leading proposals would enable trading of carbon saved by reducing tropical deforestation, just as carbon is currently traded from reducing industrial emissions. The state of these discussions suggests that a key group of countries are at risk of being omitted from a new framework—those with high forest cover and low rates of deforestation (HFLD). Developing countries can be classified into four categories defined by two axes: remaining forest cover and deforestation rate (Figure 1). The HFLD countries in Quadrant IV harbor 18% of tropical forest carbon. Since current proposals would award carbon credits to countries based on their reductions of emissions from a recent historical reference rate [4], HFLD countries could be left with little potential for RED credits. Nor would they have the potential for reforestation credits under the Kyoto Protocol's Clean Development Mechanism that the countries in Quadrant II have. Without the opportunity to sell carbon credits, HFLD countries would be deprived of a major incentive to maintain low deforestation rates. Since drivers of deforestation are mobile, deforestation reduced elsewhere could shift to HFLD countries, constituting a significant setback to stabilizing global concentrations of greenhouse gases at the lowest possible levels. Figure 1 Forests and Carbon in 80 Tropical Countries An effective RED carbon regime should not allow leaks of deforestation to new regions, but should reduce net global emissions by encouraging comprehensive changes in international behavior. Some analysts have proposed adopting a reference emission rate indexed to the global deforestation rate for countries with little or no historic deforestation [7,8]. This would effectively award HFLD countries with “preventive credits” that these countries would stand to forfeit if they were to increase their deforestation rate. Preventive credits would provide a significant entry barrier to new forest exploitation or policies that promote or allow deforestation. HFLD countries would receive a significant incentive to maintain low rates of deforestation from any reference emission rate indexed to the global average. At US$10/ton CO2, using one-third of the global average deforestation rate as the reference emission rate for HFLD countries, preventive credits would be worth US$365 million annually to seven countries. Using one-half of the global average deforestation rate as the reference rate would more than double the qualifying forest area, and would increase credit value to US$630 million annually to ten countries (Table 1). Using the global average deforestation rate as the reference rate would increase credit value to US$1.8 billion annually to 11 countries. Table 1 Estimated Annual Value of Preventive Credits Despite the advantages of crediting for HFLD countries, some practical concerns remain. Introducing an additional source of carbon credits could lower the price of carbon, weakening the incentive to reduce deforestation in countries where rates are high. However, preventive credits should be evaluated in light of their net effect in reducing global CO2 emissions. The volume of preventive credits necessary to create an advance incentive against deforestation in HFLD countries would be 10–49 million tons of carbon annually, depending on which reference rate is selected. This is equivalent to just 1.3%–6.5% of developing countries' emissions from deforestation. The greater the global demand for carbon credits, the less impact this increase in supply would have on carbon price. In return, preventive credits would extend substantial protection to nearly one-fifth of tropical forest carbon. Finally, countries like Brazil, Indonesia, and the Democratic Republic of the Congo are so large that they have regions in multiple quadrants. The Brazilian Amazon has attributes similar to the countries in Quadrant IV, and RED credits are being negotiated for the region [9]. While the quadrant approach helps identify technical gaps and policy options, in practice international responses must be tailored to individual country realities. Preventive credits are an important part of a realistic approach to quickly minimize carbon releases from loss of some of the world's most biologically important forests. Globally indexed reference emission rates for HFLD countries should be part of any international framework for reducing global carbon emissions from deforestation.

Plant Species Migration as a Key Uncertainty in Predicting Future Impacts of Climate Change on Ecosystems: Progress and Challenges

Abstract: As we show above, a failure to incorporate migration limitations into models of vegetation response to climate change greatly compromises their predictive capability, and the uncertainty due to migration is therefore substantial. Species range shifts have been a ubiquitous response by plant species during Pleistocene climate change, and early signs of this response are evident in modern assemblages. Recent work has increased our understanding of the dispersal limitations to migration rate, but there has been far less focus on the issues which govern population establishment and growth rate, especially at the edge of species’ ranges.

Monitoring effects of anthropogenic climate change on ecosystems : A role for systematic ecological observation?

Abstract: We consider here the opportunities and challenges for South Africa in long-termecological research (LTER) to detect the impacts of anthropogenic climate change on biota (as one of several competing objectives of long-term monitoring). The LTER approach has high potential for this purpose in South Africa because of a wealth of historical climate data relative to much of the African continent, and good representation of many African ecosystem types. However, there are substantial challenges to the identification and attribution of climate change impacts on African ecosystems. These are posed by climate variability at a range of time scales, the importance of rainfall rather than temperature as an ecological driver, and the significance of fire as a stochastic disturbance. An awareness of environmental and climate history will be crucial to interpreting data on trends, and sites with established historical data should be preferred for this reason. The placement of LTER sites to provide representivity of ecosystem types may unintentionally limit the detectability of climate change impacts, because change might best be detected in ecotonal or azonal environments. This could be overcome by additional experimental manipulations at LTER sites to 'force' anticipated changes and characterize species and ecosystem responses. A focus on the detection of climate change would sharpen an LTER programme's emphasis over time and provide policy advice, and science training rationales for the long term. It should especially interpret key information to decision-makers as a priority.

Spatial and temporal variation in species‐area relationships in the Fynbos biological hotspot

Abstract: Species-area relations (SARs) are among the few recognized general patterns of ecology, are empirical relations giving the number of species found within an area of a given size and were initially formulated for island environments. The use of SARs has been extended to mainland environments, and to give baseline estimates of extinction rates attending habitat loss. Using current species distributions based on atlas data, we examined the spatial variation of rates of species accumulation and species-area curves for Proteaceae species for all one-minute by one-minute areas within the Cape Floristic Region, South Africa. We compared SARs for current distributions to those generated from modeled future Protea distributions following climate change. Within one biome and for two different scales, there exists a very large spatial variation in turnover rates for current Proteaceae distributions, and we show that these rates will not remain constant as climate warming progresses. As climate changes in coming years, some areas will gain species due to migration, as other areas lose species, and still other areas maintain current rates of species accumulation/turnover. Both current and future distributions show highly variable rates of species accumulation across the landscape. This means that an average species-area relationship will hide a very large interval of variation among SARs, for both current and future Proteaceae distributions. The naive use of species-area relations to estimate species extinctions following loss of current habitat, or loss of future climatically-suitable area is likely to result in erroneous predictions.

Plant Physiological Responses to Climate and Environmental Change

Abstract: A future climate and environmental regime will affect plant physiology and induce higher order responses. Implications of rising atmospheric carbon dioxide are positive for plant growth, but less so than predicted from the theory of photosynthesis, because of feedback effects within the plant, and from ecosystem level feedback effects. Rising temperatures will reduce freezing and chill stress incidence, but warming will increase metabolic rates. High extremes will induce heat-shock responses. Higher plants are physiologically well-defended against projected increases in UV-B. Interactions between stresses will be multifaceted, but theory is poorly developed to make projections of their net result. A focus on testing theory using field-based experiments will be an important way forward. Keywords: acclimation; global change; heat shock; photosynthesis; respiration; stress

PDEMR Model in Rare Protea Count Prediction

Abstract: In this paper, we merge partial differential equation model, regression model and credibility measure based fuzzy mathematics proposed by Liu into a new partial differential equation motivated regression model (abbreviated as PDEMR model). The creation of PDEMR model further extends DEMR model ideation proposed by Guo et al. Furthermore, we develop a PDEMR model for the quantitative modeling on multivariate small sample data. PDEMR models will be able to establish the quantitative relationship among the main factor vector and the covariate vectors, which is a major improvement of information extraction with sparse data availability. Finally, we apply the PDEMR model to South African rare Protea species predictions and even tune up the data set for a regional GIS kriging maps.

Is climate prediction model flawed? : opinion

Abstract: The following was written by Dr GF Midgley and Prof LG Underhill in response to the article by Prof WRJ Alexander on his multi-year climate prediction model, which appeared in the January/February 2007 edition of the Water Wheel.

Putting it on the line

Abstract: For many people, maps are an endless source of fascination, evoking a sense of discovery, of floating above colourfully summarized and abstracted landscapes. From the dawn of exploration, maps have manifested the power of knowledge. In facing climate change, the world needs knowledge and power to counteract a debilitating helplessness. Prose can be ineffectual at communicating climate change, when the task is so daunting and the issues so multifaceted, so what better way to express this than in map form? For this reason alone, The Atlas of Climate Change, from Earthscan's State of the World atlas series, is a great addition to a burgeoning literature.