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Climatic extremes improve predictions of spatial patterns of tree species
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Understanding niche evolution, dynamics, and the response of species to climate change requires knowledge of the determinants of the environmental niche and species range limits. Mean values of climatic variables are often used in such analyses. In contrast, the increasing frequency of climate extremes suggests the importance of understanding their additional influence on range limits. Here, we assess how measures representing climate extremes (i.e., interannual variability in climate parameters) explain and predict spatial patterns of 11 tree species in Switzerland. We find clear, although comparably small, improvement (20% in adjusted D2, 8% and 3% in cross-validated True Skill Statistic and area under the receiver operating characteristics curve values) in models that use measures of extremes in addition to means. The primary effect of including information on climate extremes is a correction of local overprediction and underprediction. Our results demonstrate that measures of climate extremes are important for understanding the climatic limits of tree species and assessing species niche characteristics. The inclusion of climate variability likely will improve models of species range limits under future conditions, where changes in mean climate and increased variability are expected.
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Comment: Don’t judge species on their origins
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SUMMARY: Conservationists should assess organisms on environmental impact rather than on whether they are natives, argue Mark Davis and 18 other ecologists. FROM THE TEXT: Nativeness is not a sign of evolutionary fitness or of a species having positive effects.The insect currently suspected to be killing
more trees than any other in North Americais the native mountain pine beetle Dendroctonus ponderosae. Classifying biota according to their adherence to cultural standards of belonging, citizenship, fair play and
morality does not advance our understanding of ecology. Over the past few decades, this perspective has led many conservation and restoration efforts down paths that make little ecological or economic sense
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Conserving the Stage: Climate Change and the Geophysical Underpinnings of Species Diversity
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Conservationists have proposed methods for adapting to climate change that assume species distributions are primarily explained by climate variables. The key idea is to use the understanding of species-climate relationships to map corridors and to identify regions of faunal stability or high species turnover. An alternative approach is to adopt an evolutionary timescale and ask ultimately what factors control total diversity, so that over the long run the major drivers of total species richness can be protected. Within a single climatic region, the temperate area encompassing all of the Northeastern U.S. and Maritime Canada, we hypothesized that geologic factors may take precedence over climate in explaining diversity patterns.
If geophysical diversity does drive regional diversity, then conserving geophysical settings may offer an approach to conservation that protects diversity under both current and future climates. Here we tested how well geology predicts the species diversity of 14 US states and three Canadian provinces, using a comprehensive new spatial dataset. Results of linear regressions of species diversity on all possible combinations of 23 geophysical and climatic variables indicated that four geophysical factors; the number of geological classes, latitude, elevation range and the amount of calcareous bedrock, predicted species diversity with certainty (adj. R2 = 0.94). To confirm the species-geology relationships we ran an
independent test using 18,700 location points for 885 rare species and found that 40% of the species were restricted to a single geology. Moreover, each geology class supported 5–95 endemic species and chi-square tests confirmed that calcareous bedrock and extreme elevations had significantly more rare species than expected by chance (P,0.0001), strongly corroborating the regression model. Our results suggest that protecting geophysical settings will conserve the stage for current and future biodiversity and may be a robust alternative to species-level predictions.
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Dispersal will limit ability of mammals to track climate change in the Western Hemisphere
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As they have in response to past climatic changes, many species will shift their distributions in response to modern climate change. However, due to the unprecedented rapidity of projected climatic changes, some species may not be able to move their ranges fast enough to track shifts in suitable climates and associated habitats. Here, we investigate the ability of 493 mammals to keep pace with projected climatic changes in the Western Hemisphere. We modeled the velocities at which species will likely need to move to keep pace with projected changes in suitable climates. We compared these velocities with the velocities at which species are able to move as a function of dispersal distances and dispersal frequencies. Across the Western Hemisphere, on average, 9.2% of mammals at a given location will likely be unable to keep pace with climate change. In some places, up to 39% of mammals may be unable to track shifts in suitable climates. Eighty-seven percent of mammalian species are expected to experience reductions in range size and 20% of these range reductions will likely be due to limited dispersal abilities as opposed to reductions in the area of suitable climate. Because climate change will likely outpace the response capacity of many mammals, mammalian vulnerability to climate change may be more extensive than previously anticipated.
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Dissecting insect responses to climate warming: overwintering and post-diapause performance in the southern green stink bug, Nezara viridula, under simulated climate-change conditions
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The effect of simulated climate change on overwintering and postdiapause
reproductive performance is studied in Nezara viridula (L.) (Heteroptera:
Pentatomidae) close to the species’ northern range limit in Japan. Insects are reared
from October to June under quasi-natural (i.e. ambient outdoor) conditions and in
a transparent incubator, in which climate warming is simulated by adding 2.5 ◦
C to
the ambient temperatures. Despite the earlier assumption that females of N. viridula
overwinter in diapause, whereas males do so in quiescence, regular dissections show
that the two sexes overwinter in a state of true diapause. During winter, both sexes are
dark-coloured and have undeveloped reproductive organs. Resumption of development
does not start until late March. During winter, the effect of simulated warming on the
dynamics and timing of physiological processes appears to be limited. However, the
warming significantly enhances winter survival (from 27–31% to 47–70%), which
is a key factor in range expansion of N. viridula. In spring, the effect of simulated
warming is complex. It advances the post-diapause colour change and transition from
dormancy to reproduction. The earlier resumption of development is more pronounced
in females: in April, significantly more females are already in a reproductive state
under the simulated warming than under quasi-natural conditions. In males, the
tendency is similar, although the difference is not significant. Warming significantly
enhances spring survival and percentage of copulating adults, although not the percentage
of ovipositing females and fecundity. The results suggest that, under the expected
climate-warming conditions, N. viridula will likely benefit mostly as a result of
increased winter and spring survival and advanced post-diapause reproduction. Further
warming is likely to allow more adults to survive the critical cold season and contribute
(both numerically and by increasing heterogeneity) to the post-overwintering population
growth, thus promoting the establishment of this species in newly-colonized
area
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Ecological and Evolutionary Responses to Recent Climate Change
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Ecological changes in the phenology and distribution of plants and animals are occurring in all well-studied marine, freshwater, and terrestrial groups. These observed changes are heavily biased in the directions predicted from global warming and have been linked to local or regional climate change through correlations between climate and biological variation, field and laboratory experiments, and physiological research. Range-restricted species, particularly polar and mountaintop species, show severe range contractions and have been the first groups in which entire species have gone extinct due to recent climate change. Tropical coral reefs and amphibians have been most negatively affected. Predator-prey and plant-insect interactions have been disrupted when interacting species have responded differently to warming. Evolutionary adaptations to warmer conditions have occurred in the interiors of species’ ranges, and resource use and dispersal have evolved rapidly at expanding range margins. Observed genetic shifts modulate local effects of climate change, but there is little evidence that they will mitigate negative effects at the species level.
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Non-equilibrium succession dynamics indicate continued northern migration of lodgepole pine
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This study provides evidence of range expansion under current climatic conditions of an indigenous species with strong ecosystem effects. Surveys of stands along the northern distribution limit of lodgepole pine (Pinus contorta var. latifolia) in central Yukon Territory, Canada showed consistent increases in pine dominance following fire. These patterns differed strongly from those observed at sites where pine has been present for several thousand years. Differences in species thinning rates are unlikely to account for the observed increases in pine dominance. Rates of pine regeneration at its range limits were equivalent to those of spruce, indicating a capacity for rapid local population expansion. The study also found no evidence of strong climatic limitation of pine population growth at the northern distribution limit. We interpret these data as evidence of current pine expansion at its range limits and conclude that the northern distribution of lodgepole pine is not in equilibrium with current climate. This study has implications for our ability to predict vegetation response to climate change when populations may lag in their response to climate.
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Protected areas in Borneo may fail to conserve tropical forest biodiversity under climate change
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Protected areas (PAs) are key for conserving rainforest species, but many PAs are becoming increasingly
isolated within agricultural landscapes, which may have detrimental consequences for the forest biota
they contain. We examined the vulnerability of PA networks to climate change by examining connectivity
of PAs along elevation gradients. We used the PA network on Borneo as a model system, and examined
changes in the spatial distribution of climate conditions in future. A large proportion of PAs will not
contain analogous climates in future (based on temperature projections for 2061–2080), potentially
requiring organisms to move to cooler PAs at higher elevation, if they are to track climate changes. For
the highest warming scenario (RCP8.5), few (11–12.5%; 27–30/240) PAs were sufficiently topographically
diverse for analogous climate conditions (present-day equivalent or cooler) to remain in situ. For the
remaining 87.5–89% (210–213/240) of PAs, which were often situated at low elevation, analogous climate
will only be available in higher elevation PAs. However, over half (60–82%) of all PAs on Borneo are too
isolated for poor dispersers (<1 km per generation) to reach cooler PAs, because there is a lack of connecting
forest habitat. Even under the lowest warming scenario (RCP2.6), analogous climate conditions will
disappear from 61% (146/240) of PAs, and a large proportion of these are too isolated for poor dispersers
to reach cooler PAs. Our results suggest that low elevation PAs are particularly vulnerable to climate
change, and management to improve linkage of PAs along elevation gradients should be a conservation
priority
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Stoleson, Scott
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