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

https://www.fws.gov/southwest/es/documents/R2ES/LitCited/LPC_2012/Parmesan_2006.pdf

Ecological and Evolutionary Responses to Recent Climate Change

Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

The Intergovernmental Panel on Climate Change (IPCC) confirmed that mean global warming was 0.6 ± 0.2 °C during the 20th century and cited anthropogenic increases in greenhouse gases as the likely cause of temperature rise in the last 50 years. But this mean value conceals the substantial complexity of observed climate change, which is seasonally- and diurnally-biased, decadally-variable and geographically patchy. In particular, over the last 50 years three high-latitude areas have undergone recent rapid regional (RRR) warming, which was substantially more rapid than the global mean. However, each RRR warming occupies a different climatic regime and may have an entirely different underlying cause. We discuss the significance of RRR warming in one area, the Antarctic Peninsula. Here warming was much more rapid than in the rest of Antarctica where it was not significantly different to the global mean. We highlight climate proxies that appear to show that RRR warming on the Antarctic Peninsula is unprecedented over the last two millennia, and so unlikely to be a natural mode of variability. So while the station records do not indicate a ubiquitous polar amplification of global warming, the RRR warming on the Antarctic Peninsula might be a regional amplification of such warming. This, however, remains unproven since we cannot yet be sure what mechanism leads to such an amplification. We discuss several possible candidate mechanisms: changing oceanographic or changing atmospheric circulation, or a regional air-sea-ice feedback amplifying greenhouse warming. We can show that atmospheric warming and reduction in sea-ice duration coincide in a small area on the west of the Antarctic Peninsula, but here we cannot yet distinguish cause and effect. Thus for the present we cannot determine which process is the probable cause of RRR warming on the Antarctic Peninsula and until the mechanism initiating and sustaining the RRR warming is understood, and is convincingly reproduced in climate models, we lack a sound basis for predicting climate change in this region over the coming century.

Recent Rapid Regional Climate Warming on the Antarctic Peninsula

Global climate change is frequently considered a major conservation threat. The Earth's climate has already warmed by 0.5 8 C over the past century, and recent studies show that it is possible to detect the ef- fects of a changing climate on ecological systems. This suggests that global change may be a current and fu- ture conservation threat. Changes in recent decades are apparent at all levels of ecological organization: pop- ulation and life-history changes, shifts in geographic range, changes in species composition of communities, and changes in the structure and functioning of ecosystems. These ecological effects can be linked to recent population declines and to both local and global extinctions of species. Although it is impossible to prove that climate change is the cause of these ecological effects, these findings have important implications for conser- vation biology. It is no longer safe to assume that all of a species' historic range remains suitable. In drawing attention to the importance of climate change as a current threat to species, these studies emphasize the need for current conservation efforts to consider climate change in both in situ conservation and reintroduction efforts. Additional threats will emerge as climate continues to change, especially as climate interacts with other stressors such as habitat fragmentation. These studies can contribute to preparations for future chal- lenges by providing valuable input to models and direct examples of how species respond to climate change.

/pdf/ecological-consequences-of-recent-climate-change-1shr8t7be0.pdf

Ecological Consequences of Recent Climate Change

1. The stable isotopes of nitrogen (δ 15 N) and carbon (δ 13 C) were analysed in 22 species of marine birds from coastal waters of the northeast Pacific Ocean. Analyses confirm that stable nitrogen isotopes can predict seabird trophic positions. 2. Based on δ 15 N analyses, seabird trophic-level inferences generally agree with those of conventional dietary studies, but suggest that lower trophic-level organisms are more important to several seabirds than was recognized previously. 3. Stable-carbon isotope analysis may be a good indicator of inshore vs. offshore feeding preference

https://www.jstor.org/stable/pdfplus/5256.pdf

Using stable isotopes to determine seabird trophic relationships

A central tenet of Antarctic ecology suggests that increases in Chinstrap Penguin (Pygoscelis antarctica) populations during the last four decades resulted from an increase in prey availability brought on by the decrease in baleen whale stocks. We question this tenet and present evidence to support the hypothesis that these increases are due to a gradual decrease in the frequency of cold years with extensive winter sea ice cover resulting from environmental warming. Supporting data were derived from one of the first, major multidisciplinary winter expedition to the Scotia and Weddell seas; recent satellite images of ocean ice cover; and the analysis of long-term surface temperature records and penguin demography. Our observations indicate there is a need to pay close attention to environmental data in the management of Southern Ocean resources given the complexity of relating biological changes to ecological perturbations.

Increases in Antarctic penguin populations: reduced competition with whales or a loss of sea ice due to environmental warming?

Diet composition of the members of 2 seabird species assemblages in the Scotia-Weddell Confluence region, Antarctica, was investigated during 3 seasons/years: spring 1983, autumn 1986, and winter 1988. One assemblage frequented the pack ice and the other was present in adjacent open waters; most members of the latter species assemblage vacated the Antarctic during winter. We sought answers to 2 questions: (1) Did the 2 species assemblages depend on food webs that differed substantially; and (2) Was there a trophic basis to explain why the pack-ice assemblage did not expand into the open water left vacant by the other during winter? To test an a priori hypothesis that diet was affected by habitat, diet samples were obtained from birds encountered in 3 habitats: open water, sparse concentrations of ice, and heavy ice cover. Cluster analysis showed broad overlap in seabird diet regardless of species, habitat (ice/water mass) or year. Seabirds exploited prey largely according to ranked availability, although they appeared to choose the larger fish and crustaceans over smaller crustaceans. Myctophids in particular, but also krill and squid, were the main prey groups. Diets did not separate on the basis of predator/prey size to any appreciable degree even though a lOOO-fold difference in predator size existed. Feeding success, as indicated by fullness of stomach, of the members of the 2 species assemblages was highest when in their respective usual habitats. We conclude that open-water seabirds lack the specialized foraging behaviors required to exploit the pack-ice environ­ ment and that open waters during the winter offer much poorer feeding conditions than those of the pack ice.

/pdf/does-prey-preference-affect-habitat-choice-in-antarctic-vqogj94qfr.pdf

Does prey preference affect habitat choice in Antarctic seabirds

We quantitatively assess seasonal changes in community structure and habitat selection among seabirds in the Scotia-Weddell Confluence region, Antarctica. Additionally, we discuss the biological and physical factors underlying the patterns. Data were derived from strip-transects on closely-coordinated multidisciplinary cruises that characterized the physics and biology during spring 1983, autumn 1986 and winter 1988. We describe for the first time ever for the Southern Ocean seasonal changes in seabird communities in terms of composition, using cluster analysis, as well as relative density and diversity among species. Sea-surface temperature, distance to the pack ice edge and ice type, all physical characteristics of habitat, were the most important environmental variables that affected assemblage composition

Ecological structure among migrant and resident seabirds of the Scotia-Weddell confluence region

The foraging behaviour of fur seals and two species of surface feeding seabirds was observed over swarms of vertically migrating krill along the Antarctic Peninsula in July 1987. Fur Seal haul out patterns were correlated with krill in the upper 30 m of the water column. Krill moved to the surface at night; seals subsequently foraged from 1400-0700 hours before returning to floes. Foraging was continuous through the night. Dive duration decreased as krill moved up to the surface; shorter dives may have been more successful than longer ones. It is possible that very deep dives, which occur early in a foraging bout, represent more of an attempt to assess krill depth and distribution rather than being a genuine foraging effort. Seabirds responded to the presence of a surface krill swarm by circling over it and foraging; krill at depths greater than 30 m elicited directional flight and low frequencies of prey capture attempts. Both Snow Petrels and Antarctic Terns preyed on krill, but each species approached the swarms from different habitats. Snow Petrels primarily overflew areas covered by ice; terns preferred open water. This suggested that prey encounters are essentially opportunistic, although the search for prey is limited to rather specific marine habitats. This feature may be important to our understanding of the factors that determine the pelagic distribution of seabirds.

Seabird and fur seal responses to vertically migrating winter krill swarms in Antarctica

Using seabirds as sampling devices on two cruises in the northwestern Weddell Sea, we investigated the species and lengthfrequency distribution of micronekton in surface waters. Our micronekton samples are among the first ever collected simultaneously in both ice-covered and adjacent ice-free waters in the Antarctic using the same technique. Changes in the abundance or presence of certain crustacean, squid, and fish species were related to the presence of ice, and to distance from the ice edge. Length-frequency distributions representing age- or sex-classes of fish and krill were also affected by proximity to the ice edge. Our data indicate that the proximity of sampling to pack ice may affect our perception of the composition of micronektonic communities, and that the marginal ice zone is an important area for juvenile age-classes of pelagic fish and krill.

William R. Fraser

Papers

Increases in Antarctic penguin populations: reduced competition with whales or a loss of sea ice due to environmental warming?

Does prey preference affect habitat choice in Antarctic seabirds

Ecological structure among migrant and resident seabirds of the Scotia-Weddell confluence region

Seabird and fur seal responses to vertically migrating winter krill swarms in Antarctica

Effects of Pack Ice on the Composition of Micronektonic Communities in the Weddell Sea