Climate Change Ecology最新文献

Predicting spring phenology in temperate forests is critical for forecasting important processes such as carbon storage. One major forecasting method for phenology is the growing degree day (GDD) model, which tracks heat accumulation. Forecasts using GDD models typically assume that the GDD threshold for a species is constant across diverse landscapes, but increasing evidence suggests otherwise. Shifts in climate with anthropogenic warming may change the required GDD. Variation in climate across space may also lead to variation in GDD requirements, with recent studies suggesting that fine-scale spatial variation in climate may matter to phenology. Here, we combine simulations, observations from an urban and a rural site, and Bayesian hierarchical models to assess how consistent GDD models of budburst are across species and space. We built GDD models using two different methods to measure climate data: on-site weather stations and local dataloggers. We find that estimated GDD thresholds can vary up to 20% across sites and methods. Our results suggest our studied urban site requires fewer GDDs until budburst and may have stronger microclimate effects than the studied rural site, though these effects depend on the method used to measure climate. Further, we find that GDD models are less accurate for early-active species and may become less accurate with warming. Our results suggest that local-scale forecasts based on GDD models for spring phenology should incorporate these inherent accuracy issues of GDD models, alongside the variations we found across space, species and warming. Testing whether these issues persist at larger spatial scales could improve forecasts for temperate forests.

Sea-level rise (SLR) is expected to elevate the depth of seawater above shallow coral reefs, reducing light availability to the benthic environment, and impacting the survival and growth of corals especially on turbid reefs. However, the extent of impact at the deepest reef zones remains unknown. Coral growth could continue to keep pace above light thresholds as sea level rises, but mortality due to light limitation could vary between localities and local conditions. Here, we examine possible outcomes of corals inhabiting Singapore's turbid reefs in the years 2050 and 2100 by characterising their depth distributions and predicting potential mortality rates based on SLR projections. Our results reveal that in 2050, under both RCP4.5 and RCP8.5 sea level projections, up to 6.24% of colonies could face mortality if their growth is not considered. In 2100, up to 7.68% mortality under RCP4.5 and up to 10.7% mortality under RCP8.5 are predicted. When coral linear extension is considered, in 2050, under both RCP4.5 and RCP8.5 sea level projections, up to 1.03% of colonies could face mortality. In 2100, up to 0.87% mortality under RCP4.5 and up to 1.84% mortality under RCP8.5 are predicted. Species-specific losses could amount to 20% of colonies primarily at the deepest zones. The most vulnerable species exhibit a depth distribution with most colonies situated at the deeper parts of their depth ranges. Our findings suggest that sea-level rise may potentially result in the loss of coral cover for some species, but overall mortality could be low.

Climate change research on sea turtles has focused on the impact of rising temperatures on sex ratios, while the thermal ecology of natural nesting grounds has received less attention. Many nesting beaches are highly affected by vegetation loss and urbanization which in turn may affect their thermal profile, particularly at beaches with dark volcanic sand. We studied the sand temperatures on two urban-developed volcanic sea turtle nesting beaches in Guatemala for two years, and their potential effect on the thermal ecology of sea turtle nests by using the olive ridley as model species. We hypothesized that local weather, type of cover at surface, and season (dry vs rainy) will have a pronounced effect on sand temperatures, potentially affecting the hatching success of sea turtles. Average sand temperatures at nesting beaches were almost always above the pivotal temperature (87% of days), and either close to or above the thermal maximum tolerance of sea turtle embryos over longer periods (78% of days). We found that higher air temperatures led to higher sand temperatures, and high relative humidity and precipitation led to lower sand temperatures. As expected, sand temperatures in plots covered by vegetation were lower (32.5 ± 2.8°C) than those without vegetation cover (33.1 ± 2.6°C). Plots close to concrete structures showed the highest sand temperatures (34.0 ± 3.2°C). Our results highlight the relevance of vegetation in buffering the effects of high sand temperatures, which will have profound implications for the resilience of olive ridleys to global warming.

Climate change is altering patterns of temporal co-occurrence among species, such as the degree of co-flowering among plant species. Although much is known about how co-flowering affects pollination and plant reproduction, how these interactions are mediated by changes in abiotic conditions is unclear. Using a short-term field experiment based on a long-term flowering phenology dataset, we examine how changes in co-flowering between Linum lewisii and Potentilla pulcherrima affect the pollination and reproductive success of Linum in control and water addition scenarios. Linum is co-flowering less than it used to with Potentilla as the climate changes. We therefore removed Potentilla flowers to alter the degree of co-flowering from 0 to 100%; half of these plots received additional water to relieve drought stress. Linum plants experiencing less overlap with Potentilla had a higher proportion of conspecific pollen on their stigmas in both watered and unwatered plots. Plants experiencing less overlap also produced more seeds per plant, but only in the watering treatment. There was no evidence of pollen limitation of reproduction, but watered plants produced more seeds. These results show that plants that co-flowered to a lesser extent with Potentilla had enhanced reproductive output, probably because they received a higher proportion of Linum pollen, but these biotic effects were only detectable when the plants were less water-limited. This study provides empirical evidence that climate-driven changes in co-flowering can alter reproduction via competition for pollination, and that these biotic effects can be mediated by abiotic conditions.

Effective species conservation efforts require insight into whether a species’ extent of occurrence may shift due to changing climate, habitat loss, or both. The extent of occurrence of the threatened boreal population of woodland caribou (Rangifer tarandus caribou; caribou) has contracted due to environmental and anthropogenic disruption, with further contractions predicted as boreal habitat shifts with the changing climate. However, the direct and indirect climate drivers of caribou extent of occurrence have not been explicitly investigated. We estimated and compared the influence of climate and habitat drivers on the occurrence of caribou ranges across the Canadian boreal forest. We fit path models that estimated the direct effects of climate on caribou range occurrence and its indirect effect through climate's influence on caribou habitat (i.e., forest cover, presence of peatland, human disturbance and wildfire). Our analysis suggests that the distribution of caribou ranges is less sensitive to the direct effects of climate than to those of habitat and human disturbance. However, through its relationship to caribou habitat, climate exerts indirect influence over the distribution of caribou. As the climate changes, future distributions of caribou may be more heavily relegated to refuge habitats, particularly peatlands in the western boreal forest. Our biogeographical approach enables more informed decisions for large-scale caribou conservation efforts (e.g. establishment of protected areas, habitat restoration) that account for potential shifts in the distribution of caribou under changing environmental and climatic conditions.

The ability to track variation in climate is important for species to persist in a given environment. Lack of responses to both long-term changes and inter-annual variation in climate parameters can result in reduced fitness and population decline. Furthermore, migration strategy can influence the ability to track climatic variation due to the potential to use reliable environmental cues. Here, we studied the temporal relationship between birch leafing and onset of breeding for three bird species with contrasting migration strategies over a 20-year period in a subalpine habitat in Central Norway. We found no temporal change in birch leafing date or breeding onset for the three bird species over the study period. However, we found a statistically significant difference in the ability to track inter-annual variation in birch leafing date between the resident and two long-distance migratory species. The resident great tit Parus major was more capable of initiating egg laying in closer association to variation in birch leafing in early springs, than the long-distance migratory European pied flycatcher Ficedula hypoleuca and common redstart Phoenicurus phoenicurus. Long-distance migrants seem to have been constrained by arrival date or time from arrival to entering the breeding areas, in contrast to resident birds, which might be better able track early initiation of spring in breeding areas by adjusting egg laying date. Our findings highlight the importance of not solely studying directional long-term climatic change, but also pay attention to inter-annual variation.

The emergent responses of vulnerable species to global change can vary depending on the relative quality of resources available to support their productivity under increased stress, as well as the biotic interactions with other species that may alter their access to these resources. This research tested how seawater pCO₂ may interact with seasonal light availability to affect the photosynthesis and calcification of high-latitude coralline algae, and whether the responses of these calcified macroalgae are modified by physical association with a non-calcified seaweed. Through an in situ approach, our study first investigated how current seasonal environmental variation affects the growth of the understory coralline algae Crusticorallina spp. and Bossiella orbigniana in Southeast Alaska's kelp forests. We then experimentally manipulated pH to simulate end-of-century acidification scenarios, light regime to simulate seasonal light availability at the benthos, and pairings of coralline algal species with and without a fleshy red alga to examine the interactive effects of these variables on coralline productivity and calcification. Our results indicate that: 1) coralline species may face net dissolution under projected future winter pH and carbonate saturation state conditions, 2) differences in seasonal light availability in productive, high-latitude waters may not be distinct enough to modify coralline algal net calcification, and 3) association with a non-calcified red alga does not alter the response of these coralline algal species to ocean acidification scenarios. This research highlights the necessity of incorporating locally informed scenarios of environmental variability and community interactions when predicting species’ vulnerability to global change.

Climate change driven extreme events such as marine heatwaves (MHWs) can have dramatic impacts on ecosystems, with thermal stress often resulting in localised die-offs and visible signs of impacts such as bleaching of organisms. Such impacts are reported widely in shallower ecosystems but are less studied on deeper mesophotic ecosystems (MEs) where collecting data is more expensive. However, these deeper ecosystems are often biodiverse and play important ecological roles, and so understanding climate change impacts at these depths is important. Here we use benthic imagery collected as part of a large-scale monitoring program to explore bleaching in a cup sponge ‘morphospecies’ (i.e. morphologically distinct organisms readily identified in imagery) in MEs across eastern Tasmania, a region experiencing rapid ocean warming. We find an increased incidence of bleaching in surveys following MHWs, but currently no evidence for mass mortality following bleaching. Our results suggest that this cup sponge morphospecies may be useful for tracking climate change impacts on MEs in the region. Future efforts should be directed towards a better understanding of the physiological limits of this morphospecies across its range and timing surveys to more closely follow MHW events. Sponges form an important and dominant component of temperate MEs and monitoring the impacts of climate change on sponges across these ecosystems should therefore be an ongoing priority.

Climate change and disease are threats to biodiversity that may compound and interact with one another in ways that are difficult to predict. White-nose syndrome (WNS), caused by a cold-loving fungus (Pseudogymnoascus destructans), has had devastating impacts on North American hibernating bats, and impact severity has been linked to hibernaculum microclimate conditions. As WNS spreads across the continent and climate conditions change, anticipating these stressors’ combined impacts may improve conservation outcomes for bats. We build on the recent development of winter species distribution models for five North American bat species, which used a hybrid correlative-mechanistic approach to integrate spatially explicit winter survivorship estimates from a bioenergetic model of hibernation physiology. We apply this bioenergetic model given the presence of P. destructans, including parameters capturing its climate-dependent growth as well as its climate-dependent effects on host physiology, under both current climate conditions and scenarios of future climate change. We then update species distribution models with the resulting survivorship estimates to predict changes in winter hibernacula suitability under future conditions. Exposure to P. destructans is generally projected to decrease bats’ winter occurrence probability, but in many areas, changes in climate are projected to lessen the detrimental impacts of WNS. This rescue effect is not predicted for all species or geographies and may arrive too late to benefit many hibernacula. However, our findings offer hope that proactive conservation strategies to minimize other sources of mortality could allow bat populations exposed to P. destructans to persist long enough for conditions to improve.

Climate change scenarios predict an increase in global temperature and sea level rise. For sea turtles, the association between sea level rise, nest water content and temperature along the beach may influence embryo development and offspring survival. Over three consecutive years (2016 – 2018), a field experiment was conducted on Boa Vista island, Cabo Verde, to assess the potential impacts of tidal inundation on hatching success and hatchling phenotype in loggerhead sea turtles (Caretta caretta). Ninety-three groups of three nests each (N = 279) were relocated to a 5 km stretch of the same beach. Nests in each group were placed at regular intervals of 30 to 60 m across three zones of the beach: the lower “wet” zone, where tidal inundation was a risk, a middle zone, and the upper vegetated zone. Mean emergence and hatching success in the wet treatment was 12.0% and 18.9% respectively. In the middle zone it was 25.6% and 39.5%. In the vegetated zone it was 47.2% and 57.1%. Male hatchling production was severely reduced in the wet zone, probably by nest inundation, with the few hatchlings produced being predominantly male. Female body size and clutch size both had a significant impact on hatchling production and hatchling phenotype. In response to increased global temperatures, male hatchling production may continue in nests laid in areas of high flooding risk. The relocation of clutches to the upper beach areas as a conservation plan could be implemented to reduce the mortality of nests by high tide.