Climate change resilience of a globally important sea turtle nesting population

Few studies have looked into climate change resilience of populations of wild animals. We use a model higher vertebrate, the green sea turtle, as its life history is fundamentally affected by climatic conditions, including temperature‐dependent sex determination and obligate use of beaches subject to sea level rise (SLR). We use empirical data from a globally important population in West Africa to assess resistance to climate change within a quantitative framework. We project 200 years of primary sex ratios (1900–2100) and create a digital elevation model of the nesting beach to estimate impacts of projected SLR. Primary sex ratio is currently almost balanced, with 52% of hatchlings produced being female. Under IPCC models, we predict: (a) an increase in the proportion of females by 2100 to 76%–93%, but cooler temperatures, both at the end of the nesting season and in shaded areas, will guarantee male hatchling production; (b) IPCC SLR scenarios will lead to 33.4%–43.0% loss of the current nesting area; (c) climate change will contribute to population growth through population feminization, with 32%–64% more nesting females expected by 2120; (d) as incubation temperatures approach lethal levels, however, the population will cease growing and start to decline. Taken together with other factors (degree of foraging plasticity, rookery size and trajectory, and prevailing threats), this nesting population should resist climate change until 2100, and the availability of spatial and temporal microrefugia indicates potential for resilience to predicted impacts, through the evolution of nest site selection or changes in nesting phenology. This represents the most comprehensive assessment to date of climate change resilience of a marine reptile using the most up‐to‐date IPCC models, appraising the impacts of temperature and SLR, integrated with additional ecological and demographic parameters. We suggest this as a framework for other populations, species and taxa.     

Resilience of ecosystem processes: a new approach shows that functional redundancy of biological control services is reduced by landscape simplification

Functional redundancy can increase the resilience of ecosystem processes by providing insurance against species loss and the effects of abundance fluctuations. However, due to the difficulty of assessing individual species’ contributions and the lack of a metric allowing for a quantification of redundancy within communities, few attempts have been made to estimate redundancy for individual ecosystem processes. We present a new method linking interaction metrics with metabolic theory that allows for a quantification of redundancy at the level of ecosystem processes. Using this approach, redundancy in the predation on aphids and other prey by natural enemies across a landscape heterogeneity gradient was estimated. Functional redundancy of predators was high in heterogeneous landscapes, low in homogeneous landscapes and scaled with predator specialisation. Our approach allows quantifying functional redundancy within communities and can be used to assess the role of functional redundancy across a wide variety of ecosystem processes and environmental factors.     

Response of Amazonian forests to mid-Holocene drought: A model-data comparison

There is a major concern for the fate of Amazonia over the coming century in the face of anthropogenic climate change. A key area of uncertainty is the scale of rainforest dieback to be expected under a future, drier climate. In this study, we use the middle Holocene (ca. 6000 years before present) as an approximate analogue for a drier future, given that palaeoclimate data show much of Amazonia was significantly drier than present at this time. Here, we use an ensemble of climate and vegetation models to explore the sensitivity of Amazonian biomes to mid-Holocene climate change. For this, we employ three dynamic vegetation models (JULES, IBIS, and SDGVM) forced by the bias-corrected mid-Holocene climate simulations from seven models that participated in the Palaeoclimate Modelling Intercomparison Project 3 (PMIP3). These model outputs are compared with a multi-proxy palaeoecological dataset to gain a better understanding of where in Amazonia we have most confidence in the mid-Holocene vegetation simulations. A robust feature of all simulations and palaeodata is that the central Amazonian rainforest biome is unaffected by mid-Holocene drought. Greater divergence in mid-Holocene simulations exists in ecotonal eastern and southern Amazonia. Vegetation models driven with climate models that simulate a drier mid-Holocene (100–150 mm per year decrease) better capture the observed (palaeodata) tropical forest dieback in these areas. Based on the relationship between simulated rainfall decrease and vegetation change, we find indications that in southern Amazonia the rate of tropical forest dieback was ~125,000 km² per 100 mm rainfall decrease in the mid-Holocene. This provides a baseline sensitivity of tropical forests to drought for this region (without human-driven changes to greenhouse gases, fire, and deforestation). We highlight the need for more palaeoecological and palaeoclimate data across lowland Amazonia to constrain model responses.     

Direct and indirect impacts of wildfire on faunal communities of Mediterranean temporary ponds

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Assessing vegetation recovery from energy development using a dynamic reference approach

Ecologically relevant references are useful for evaluating ecosystem recovery, but references that are temporally static may be less useful when environmental conditions and disturbances are spatially and temporally heterogeneous. This challenge is particularly acute for ecosystems dominated by sagebrush (Artemisia spp.), where communities may require decades to recover from disturbance. We demonstrated application of a dynamic reference approach to studying sagebrush recovery using three decades of sagebrush cover estimates from remote sensing (1985–2018). We modelled recovery on former oil and gas well pads (n = 1200) across southwestern Wyoming, USA, relative to paired references identified by the Disturbance Automated Reference Toolset. We also used quantile regression to account for unmodelled heterogeneity in recovery, and projected recovery from similar disturbance across the landscape. Responses to weather and site‐level factors often differed among quantiles, and sagebrush recovery on former well pads increased more when paired reference sites had greater sagebrush cover. Little (<5%) of the landscape was projected to recover within 100 years for low to mid quantiles, and recovery often occurred at higher elevations with cool and moist annual conditions. Conversely, 48%–78% of the landscape recovered quickly (within 25 years) for high quantiles of sagebrush cover. Our study demonstrates advantages of using dynamic reference sites when studying vegetation recovery, as well as how additional inferences obtained from quantile regression can inform management.     

Focus: The Science of Stress: Potential Societal and Cultural Implications of Transgenerational Epigenetic Methylation of Trauma and PTSD: Pathology or Resilience?

Psychological trauma is unique in that it is an environmental event that could induce biological changes and post-traumatic stress disorder (PTSD), depression, or other mood disorders in some patients. On the other hand, there may be no psychopathology (in most cases), or even sometimes post-traumatic growth and resilience. According to the DSM-5, trauma is a prerequisite for PTSD and traumatic stress disorder, but not for depressive episodes or mood disorders, or other psychiatric conditions. This paper brings attention to the preliminary literature on transgenerational inheritance due to trauma exposure and its societal and cultural implications. There is accumulating evidence that exposure to trauma can be passed transgenerationally through epigenetic inheritance leading to changes in gene expression and possible disorders or resilience. The effects of resilience from transgenerational inheritance have not been studied, but should be, for a full understanding not only of the disease risk across generations, but also of its social and cultural implications. The epigenetic pathologic effects across generations also need further studies, as the current research is preliminary; larger replications are needed for definitive and more complete understanding. I present here a glimpse of where we are, a vision of where we should go in terms of future research direction for disease risk transmission, and recommend studies of resilience and post-traumatic growth across generations, as well as other studies related to the societal implications at the population level.     

Measuring Functional Diversity in Plant Communities with MixedLife Forms: A Problem of Hardand Soft Attributes

This paper examines the functional relationships among species in an Australian rangeland community with mixed life forms. It follows a previous study (Walker and others 1999) that explored the role of dominant and minor species in maintaining functional diversity and resilience in a rangeland ecosystem. Unlike our previous results, which were based on estimates of five plant functional attributes, the dominant species in this second community apparently are functionally no more dissimilar to each other than to all other species. We suggest that the lack of clear results in mixed life form communities represents a confounding of the relationships between the “hard” attributes that actually govern how a plant performs in an ecosystem and the “soft” attributes that we use as surrogates. There are very few data on the hard functional attributes of plant species and consequently little information on precisely how the (soft) measurable traits are related to their imputed functions. What evidence there is shows that although the relationships are strong within life forms, they differ between life forms. This poses a problem for the development of research relating plant biodiversity to ecosystem function. Until such a database is developed, it will be very difficult to advance our understanding and measurement of functional diversity in mixed life form communities. Received 30 April 2001; Accepted 23 January 2002.     

Contrasting Effects of Fire on Arboreal and Ground‐Dwelling Ant Communities of a Neotropical Savanna

Ants are a dominant group in tropical savannas and here we examined the responses of the arboreal and ground‐dwelling ant fauna to a fire in a Neotropical savanna (cerrado) reserve in Central Brazil. Ants were collected using pitfall traps and baits placed in trees and on the ground beneath each tree. Of the 36 trees marked along two transects, half (from each transect) were burned and half not. The same trees were sampled 1 wk before and again 3 and 12 mo after the fire. Rarefaction curves and ordination analyses using data from all trees from each side of each transect indicated that overall ant species richness and composition did not change after fire. Fire, however, reduced the mean number of ant species per tree, and increased the mean number of species on the ground. Fire increased the average abundance of specialist predators, Camponotini, and opportunistic species, and decreased that of arboreal specialists. Changes in the ground‐dwelling fauna were only detected 12 mo after the fire, while those in the arboreal fauna occurred earlier and were no longer apparent 12 mo after the fire. We suggest that these contrasting results represent mainly an indirect response of the ant communities to fire‐induced changes in vegetation. Given the temporary and small scale nature of the effects detected and the overall resilience of the ant fauna, our results indicate that a single fire in the cerrado vegetation does not greatly impact the structure of ant communities in the short term.