Landscape Partnership Resources Library
Is Global Warming Causing More, Larger Wildfires?
Higher spring and summer temperatures and earlier snowmelt are extending the wildfire season and increasing the intensity of wildfires in the western United States.
Road network density correlated with increased lightning fire incidence in the Canadian western boreal forest
This paper quantifies the influence of anthropogenic linear disturbances on fire ignition frequency in the boreal forests of western Canada. Specifically, we tested if linear features increase the frequency of lightning fires, and whether this relationship is affected by spatial resolution. We considered fires that ignited between 1995 and 2002 within a ∼67 000 km2 region of boreal mixed-wood forest in north-eastern Alberta where linear features are highly abundant and spatially heterogeneous. We constructed Poisson, Negative Binomial and Zero-Inflated Poisson models at two spatial resolutions (∼10 000 and ∼2400 ha), including covariates for linear feature densities, forest composition, weather–lightning indices and geography. We found a positive association between lightning fire frequency and road density; this association was consistent at both spatial resolutions. We suggest this occurs owing to increased availability of flammable fine fuels near roads. The effect was attributable neither to increased detectability of fires proximal to roads by human observers, nor to increased lightning strikes due to metallic infrastructure alongside roads or the topographic characteristics of road location. Our results suggest that, in the face of projected road developments in the region, the potential exists for important changes to the regional fire regime. Further research should elucidate the precise mechanisms in order to develop methods for mitigation.
Large Woody Debris and Salmonid Habitat in the Anchor River Basin, Alaska
A widespread and intense spruce beetle outbreak during the 1990s has killed most of the mature white spruce (Picea glauca) trees across many watersheds in south-central Alaska. To investigate the potential habitat impacts in a salmon stream, we characterized the current abundance and species composition of large woody debris (LWD), examined the linkages between LWD and salmonid habitat, and estimated changes in LWD abundance and associated pool habitat over time. LWD abundance was relatively low (97 pieces/km overall) and varied widely according to riparian vegetation typology, ranging from 15 pieces/km at sites with non- forested riparian zones to 170 pieces/km at sites adjacent to cottonwood forest. LWD provided significant fish cover in pools, especially in cottonwood forest stream reaches. LWD-formed pools were relatively rare (15% of total), but LWD abundance explained much of the variation in pool frequency (r2 = 0.86 in spruce forest reaches) and in the proportion of pool habitats (r2 = 0.85 in cottonwood forest reaches). We project the spruce beetle outbreak to result in a substantial net increase in LWD abundance over a 50-year span, peaking with 243% and 179% increases in LWD abundance for spruce forest and cottonwood forest stream reaches, respectively, in the year 2025. Concurrent with the peak in LWD abundance, our estimates show pool frequency in spruce forest reaches to reach 207% of current levels and the proportion of pools in cottonwood forest reaches to reach 167% of current levels, changes that correspond with substantially increased potential habitat for juvenile salmonids.
Habitat Refugia: A Practical Strategy to Conserve Biodiversity Under Climate Change
As climatic zones shift under climate change, many regions and habitats will slowly become climatically unsuit- able for some of the species that currently inhabit them. The availability of climate refugia - habitats and regions which are buffered from extremes in temperature and fluctuations in water availability, could allow some species to adapt to climate change in-situ, and facilitate dispersal and range shifts for other species. This information sheet explains the concepts behind habitat refugia with specific reference to how refugia can be used to protect and conserve terrestrial biodiversity faced with rapid climate change.
Refugia: identifying and understanding safe havens for biodiversity under climate change
Identifying and protecting refugia is a priority for conservation under pro- jected anthropogenic climate change, because of their demonstrated ability to facilitate the survival of biota under adverse conditions. Refugia are habitats that components of biodiversity retreat to, persist in and can potentially expand from under changing environmental conditions. However, the study and discussion of refugia has often been ad hoc and descriptive in nature. We therefore: (1) provide a habitat-based concept of refugia, and (2) evaluate methods for the identification of refugia.
Identifying refugia from climate change
This article highlights how the loose definition of the term ‘refugia’ has led to discrepancies in methods used to assess the vulnerability of species to the current trend of rising global temperatures. The term ‘refugia’ is commonly used without distinguishing between macrorefugia and microrefugia, ex situ refugia and in situ refugia, glacial and interglacial refugia or refugia based on habitat stability and refugia based on climatic stability. It is not always clear which definition is being used, and this makes it difficult to assess the appropriateness of the methods employed. For example, it is crucial to develop accurate fine-scale climate grids when identifying microrefugia, but coarse-scale macroclimate might be adequate for determining macrorefugia. Similarly, identifying in situ refugia might be more appropriate for species with poor dispersal ability but this may overestimate the extinction risk for good dispersers. More care needs to be taken to properly define the context when referring to refugia from climate change so that the validity of methods and the conservation significance of refugia can be assessed. Keywords Bioclimatic envelope models, climatic stability, conservation biogeography, cryptic refugia, ecological niche models, extinction risk, interglacial refugia, macrorefugia, microclimate, microrefugia.
The New Era Of Climate Risk Disclosure
In February of this year, the U.S. Securities and Exchange Commission made clear in no uncertain terms that corporations have a duty to disclose risks faced through poten- tial climate change. Yet many boards remain unaware of what constitutes a “material” climate risk, or just how broad the scope and potential impact truly are.
The impact of climate change on mental health
Climate change will shortly be assuming centre stage when Copenhagen hosts the United Nations Climate Change Conference in early December 2009. In Copenhagen, delegates will discuss the international response to climate change (i.e. the ongoing increase in the Earth’s average surface temperature) and the meeting is widely viewed as the most important of its kind ever held (http://en.cop15.dk/). International agreement will be sought on a treaty to replace the 1997 Kyoto Protocol. At the time of writing it is not known whether agreement will be reached on the main issues of reducing greenhouse gas emissions and financing the impacts of climate change, and it appears that the impact of climate change on mental health is unlikely to be on the agenda. We discuss here how climate change could have consequences for global mental health and consider the implications for future research and policy. Key words : Climate, mental disorder, mental health, global warming.
Importance of matrix habitats in maintaining biological diversity
Matrix management matters because formal reserve systems will never cover more than a small fraction of the globe.
The impact of climate change on the structure of Pleistocene food webs across the mammoth steppe
Species interactions form food webs, impacting community structure and, potentially, ecological dynamics. It is likely that global climatic perturbations that occur over long periods of time have a significant influence on species interaction patterns. Here, we integrate stable isotope analysis and network theory to reconstruct patterns of trophic interactions for six independent mammalian communities that inhabited mammoth steppe environments spanning western Europe to eastern Alaska (Beringia) during the Late Pleis- tocene. We use a Bayesian mixing model to quantify the contribution of prey to the diets of local predators, and assess how the structure of trophic inter- actions changed across space and the Last Glacial Maximum (LGM), a global climatic event that severely impacted mammoth steppe communities. We find that large felids had diets that were more constrained than those of co-occurring predators, and largely influenced by an increase in Rangifer abun- dance after the LGM. Moreover, the structural organization of Beringian and European communities strongly differed: compared with Europe, species inter- actions in Beringian communities before—and possibly after—the LGM were highly modular. We suggest that this difference in modularity may have been driven by the geographical insularity of Beringian communities.
Why a collapse of global civilization will be avoided: a comment on Ehrlich & Ehrlich
1st paragraph: Ehrlich FRS & Ehrlich [1] claim that over-population, over-consumption and the future climate mean that ‘preventing a global collapse of civilization is perhaps the foremost challenge confronting humanity’. What is missing from the well- referenced perspective of the potential downsides for the future of humanity is any balancing assessment of the progress being made on these three chal- lenges (and the many others they cite by way of detail) that suggests that the problems are being dealt with in a way that will not require a major disruption to the human condition or society. Earlier dire predictions have been made in the same mode by Malthus FRS [2] on food security, Jevons FRS [3] on coal exhaustion, King FRS & Murray [4] on peak oil, and by many others. They have all been overcome by the exercise of human ingenuity just as the doom was being prophesied with the deployment of steam engines to greatly improve agricultural efficiency, and the discoveries of oil and of fracking oil and gas, respectively, for the three examples given. It is incumbent on those who would continue to predict gloom to learn from history and make a comprehen- sive review of human progress before coming to their conclusions. The problems as perceived today by Ehrlich FRS and Ehrlich will be similarly seen off by work in progress by scientists and engineers. My comment is intended to summarize and reference the potential upsides being produced by today’s human ingenuity, and I leave the reader to weigh the balance for the future, taking into account the lessons of recent history.
Future collapse: how optimistic should we be?
1st paragraph: Prof. Kelly FRS is optimistic about the chances of avoiding a collapse, but sadly we find his arguments entirely unpersuasive. For example, have Malthus (or we) really been wrong about food security? Roughly 850 million people are seriously undernourished (lacking sufficient calories) today, and perhaps 2 billion are malnourished (lacking one or more essential nutrients) [1]. When Malthus lived, there were only about 1 billion people on the planet. We agree that there are many things that could be done to feed today’s population of 7.1 billion, or even perhaps over 9 billion in 2050. Many of them (e.g. limiting waste) have been discussed for 50 years with little sign of progress. We do not think any serious analyst doubts that, if it were equitably distributed, today’s food production could nourish everyone adequately. Equally, we know of no serious analyst who believes such distribution is likely in the future. The concern is that climate disruption combined with other problems with the agricultural system will make it impossible to feed an ever larger future population, even if equal distribution were achieved. That concern is reinforced by the recent observation that, even before the likely heavy impacts of climate disruption on agriculture appear, production is failing to keep pace with projected needs [2].
Life history predicts risk of species decline in a stochastic world
Understanding what traits determine the extinction risk of species has been a long-standing challenge. Natural populations increasingly experience reductions in habitat and population size concurrent with increasing novel environmental variation owing to anthropogenic disturbance and climate change. Recent studies show that a species risk of decline towards extinction is often non-random across species with differ- ent life histories. We propose that species with life histories in which all stage-specific vital rates are more evenly important to population growth rate may be less likely to decline towards extinction under these pressures. To test our prediction, we modelled declines in population growth rates under simulated stochas- tic disturbance to the vital rates of 105 species taken from the literature. Populations with more equally important vital rates, determined using elasticity analysis, declined more slowly across a gradient of increas- ing simulated environmental variation. Furthermore, higher evenness of elasticity was significantly correlated with a reduced chance of listing as Threatened on the International Union for Conservation of Nature Red List. The relative importance of life-history traits of diverse species can help us infer how natural assemblages will be affected by novel anthropogenic and climatic disturbances. Keywords: International Union for Conservation of Nature Red List; extinction; life history; stage-based; elasticity; stochasticity
On a collision course: competition and dispersal differences create no-analogue communities and cause extinctions during climate change
Most climate change predictions omit species interactions and interspecific variation in dispersal. Here, we develop a model of multiple competing species along a warming climatic gradient that includes temperature- dependent competition, differences in niche breadth and interspecific differences in dispersal ability. Competition and dispersal differences decreased diversity and produced so-called ‘no-analogue’ commu- nities, defined as a novel combination of species that does not currently co-occur. Climate change altered community richness the most when species had narrow niches, when mean community-wide dispersal rates were low and when species differed in dispersal abilities. With high interspecific dispersal variance, the best dispersers tracked climate change, out-competed slower dispersers and caused their extinction. Overall, competition slowed the advance of colonists into newly suitable habitats, creating lags in climate tracking. We predict that climate change will most threaten communities of species that have narrow niches (e.g. tropics), vary in dispersal (most communities) and compete strongly. Current forecasts probably underestimate climate change impacts on biodiversity by neglecting competition and dispersal differences. Keywords: climate change; competition; dispersal; community ecology; movement ecology; thermal performance breadth
Genetic change for earlier migration timing in a pink salmon population
To predict how climate change will influence populations, it is necessary to understand the mechanisms, particularly microevolution and phenotypic plasticity, that allow populations to persist in novel environmental conditions. Although evidence for climate-induced phenotypic change in populations is widespread, evidence documenting that these phenotypic changes are due to microevolution is exceed- ingly rare. In this study, we use 32 years of genetic data (17 complete generations) to determine whether there has been a genetic change towards earlier migration timing in a population of pink salmon that shows phenotypic change; average migration time occurs nearly two weeks earlier than it did 40 years ago. Experimental genetic data support the hypothesis that there has been directional selection for earlier migration timing, resulting in a substantial decrease in the late-migrating phenotype (from more than 30% to less than 10% of the total abundance). From 1983 to 2011, there was a significant decrease—over threefold—in the frequency of a genetic marker for late-migration timing, but there were minimal changes in allele frequencies at other neutral loci. These results demonstrate that there has been rapid microevolution for earlier migration timing in this population. Circadian rhythm genes, however, did not show any evidence for selective changes from 1993 to 2009. Keywords: microevolution; genetic change; salmon; circadian rhythms; climate change; migration timing
How the type of anthropogenic change alters the consequences of ecological traps
Understanding altered ecological and evolutionary dynamics in novel environments is vital for predicting species responses to rapid environmental change. One fundamental concept relevant to such dynamics is the ecological trap, which arises from rapid anthropogenic change and can facilitate extinction. Ecological traps occur when formerly adaptive habitat preferences become maladaptive because the cues individuals preferentially use in selecting habitats lead to lower fitness than other alternatives. While it has been emphasized that traps can arise from different types of anthropogenic change, the resulting consequences of these different types of traps remain unknown. Using a novel model framework that builds upon the Price equation from evolutionary genetics, we provide the first analysis that contrasts the ecological and evolutionary consequences of ecological traps arising from two general types of perturbations known to trigger traps. Our model suggests that traps arising from degradation of existing habitats are more likely to facilitate extinction than those arising from the addition of novel trap habitat. Importantly, our framework reveals the mechanisms of these outcomes and the substantial scope for persistence via rapid evolution that may buffer many populations from extinction, helping to resolve the paradox of continued persistence of many species in dramatically altered landscapes. Keywords: attractive sink; evolutionary trap; habitat selection; maladaptation; Price equation; rapid evolution
How does climate change cause extinction?
Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven ident- ified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relation- ship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies. Keywords: climate change; extinction; physiological tolerances; species interactions
Genetic consequences of climate change for northern plants
Climate change will lead to loss of range for many species, and thus to loss of genetic diversity crucial for their long-term persistence. We analysed range-wide genetic diversity (amplified fragment length poly- morphisms) in 9581 samples from 1200 populations of 27 northern plant species, to assess genetic consequences of range reduction and potential association with species traits. We used species distri- bution modelling (SDM, eight techniques, two global circulation models and two emission scenarios) to predict loss of range and genetic diversity by 2080. Loss of genetic diversity varied considerably among species, and this variation could be explained by dispersal adaptation (up to 57%) and by genetic differentiation among populations (FST; up to 61%). Herbs lacking adaptations for long-distance disper- sal were estimated to lose genetic diversity at higher rate than dwarf shrubs adapted to long-distance dispersal. The expected range reduction in these 27 northern species was larger than reported for tem- perate plants, and all were predicted to lose genetic diversity according to at least one scenario. SDM combined with FST estimates and/or with species trait information thus allows the prediction of species’ vulnerability to climate change, aiding rational prioritization of conservation efforts. Keywords: conservation genetics; FST; genetic diversity; range reduction; species distribution model; species traits
Rising atmospheric carbon dioxide concentration and the future of C 4 crops for food and fuel
Crops with the C4 photosynthetic pathway are vital to global food supply, particularly in the tropical regions where human well-being and agricultural productivity are most closely linked. While rising atmospheric [CO2 ] is the driving force behind the greater temperatures and water stress, which threaten to reduce future crop yields, it also has the potential to directly benefit crop physiology. The nature of C4 plant responses to elevated [CO2 ] has been controversial. Recent evidence from free-air CO2 enrichment (FACE) experiments suggests that elevated [CO2] does not directly stimulate C4 photosynthesis. Nonetheless, drought stress can be ameliorated at elevated [CO2] as a result of lower stomatal conductance and greater intercellular [CO2]. Therefore, unlike C3 crops for which there is a direct enhancement of photosynthesis by elevated [CO2 ], C4 crops will only benefit from elevated [CO2 ] in times and places of drought stress. Current projections of future crop yields have assumed that rising [CO2] will directly enhance photosynthesis in all situations and, therefore, are likely to be overly optimistic. Additional experiments are needed to evaluate the extent to which amelioration of drought stress by elevated [CO2 ] will improve C4 crop yields for food and fuel over the range of C4 crop growing conditions and genotypes.
Slow Recovery from Perturbations as a Generic Indicator of a Nearby Catastrophic Shift
The size of the basin of attraction in ecosystems with alternative stable states is often referred to as “ecological resilience.” Ecosystems with a low ecological resilience may easily be tipped into an alternative basin of attraction by a stochastic event. Unfortunately, it is very difficult to measure ecological resilience in practice. Here we show that the rate of recovery from small perturbations (some- times called “engineering resilience”) is a remarkably good indicator of ecological resilience. Such recovery rates decrease as a catastrophic regime shift is approached, a phenomenon known in physics as “crit- ical slowing down.” We demonstrate the robust occurrence of critical slowing down in six ecological models and outline a possible ex- perimental approach to quantify differences in recovery rates. In all the models we analyzed, critical slowing down becomes apparent quite far from a threshold point, suggesting that it may indeed be of practical use as an early warning signal. Despite the fact that critical slowing down could also indicate other critical transitions, such as a stable system becoming oscillatory, the robustness of the phenomenon makes it a promising indicator of loss of resilience and the risk of upcoming regime shifts in a system. Keywords: alternative stable states, catastrophic bifurcations, critical slowing down, early warning signals, resilience, return time.
