Aim A major issue in ecology, biogeography, conservation biology and invasion biology is the extent to which climate, and hence climate change, contributes to the positions of species’ range boundaries. Thirty years of rapid climate warming provides an excellent opportunity to test the hypothesis that climate acts as a major constraint on range boundaries, treating anthropogenic climate change as a large-scale experiment.

Location  UK and global data, and literature.

Methods  This article analyses the frequencies with which species have responded to climate change by shifting their range boundaries. It does not consider abundance or other changes.

Results  For the majority of species, boundaries shifted in a direction that is concordant with being a response to climate change; 84% of all species have expanded in a polewards direction as the climate has warmed (for the best data available), which represents an excess of 68% of species after taking account of the fact that some species may shift in this direction for non-climatic reasons. Other data sets also show an excess of animal range boundaries expanding in the expected direction.

Main conclusions  Climate is likely to contribute to the majority of terrestrial and freshwater range boundaries. This generalization excludes species that are endemic to specific islands, lakes, rivers and geological outcrops, although these local endemics are not immune from the effects of climate change. The observed shifts associated with recent climate change are likely to have been brought about through both direct and indirect (changes to species’ interactions) effects of climate; indirect effects are discussed in relation to laboratory experiments and invasive species. Recent observations of range boundary shifts are consistent with the hypothesis that climate contributes to, but is not the sole determinant of, the position of the range boundaries of the majority of terrestrial animal species.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1472-4642.2010.00642.x

Climate, climate change and range boundaries

The effects of climate change on tropical birds

Despite awareness that disease emergence may be related to ecological change, few studies have rigorously analyzed the underlying environmental drivers of the dynamics of disease emergence. This may be due to the fact that ecological change and disease emergence are often mediated through complex and large-scale processes that are not amenable to traditional reductionist approaches to causal inference. Here, we suggest strategies assembled from diverse disciplines, including ecology, epidemiology, and the social sciences, to analyze complex relationships, promote cooperation, increase efficiency, and minimize bias when investigating the ecological drivers of disease emergence. These techniques, which complement traditional hypothesis testing, include epidemiologic causal criteria, strong inference, causal diagrams, model selection, and triangulation. We also present several examples from recent emerging infectious disease investigations, including Hendra virus, Nipah virus, coral diseases, and avian influenza, where these techniques were successfully applied. Here, we outline some of the barriers to advancing our understanding of causation in disease ecology and offer some solutions for investigating large-scale ecological drivers, such as global warming, pollution, and land-use change.

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/070086

Causal inference in disease ecology: investigating ecological drivers of disease emergence

Arguably one of the most important effects of climate change is the potential impact on human health. While this is likely to take many forms, the implications for future transmission of vector-borne diseases (VBDs), given their ongoing contribution to global disease burden, are both extremely important and highly uncertain. In part, this is owing not only to data limitations and methodological challenges when integrating climate-driven VBD models and climate change projections, but also, perhaps most crucially, to the multitude of epidemiological, ecological and socio-economic factors that drive VBD transmission, and this complexity has generated considerable debate over the past 10–15 years. In this review, we seek to elucidate current knowledge around this topic, identify key themes and uncertainties, evaluate ongoing challenges and open research questions and, crucially, offer some solutions for the field. Although many of these challenges are ubiquitous across multiple VBDs, more specific issues also arise in different vector–pathogen systems.

https://digitalcommons.odu.edu/cgi/viewcontent.cgi?article=1326&context=biology_fac_pubs

Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission

Avian malaria is a worldwide mosquito-borne disease caused by Plasmodium parasites. These parasites occur in many avian species but primarily affect passerine birds that have not evolved with the parasite. Host pathogenicity, fitness, and population impacts are poorly understood. In contrast to continental species, introduced avian malaria poses a substantial threat to naive birds on Hawaii, the Galapagos, and other archipelagoes. In Hawaii, transmission is maintained by susceptible native birds, competence and abundance of mosquitoes, and a disease reservoir of chronically infected native birds. Although vector habitat and avian communities determine the geographic distribution of disease, climate drives transmission patterns ranging from continuous high infection in warm lowland forests, seasonal infection in midelevation forests, and disease-free refugia in cool high-elevation forests. Global warming is expected to increase the occurrence, distribution, and intensity of avian malaria across this elevational gradient and threaten high-elevation refugia, which is the key to survival of many susceptible Hawaiian birds. Increased temperatures may have already increased global avian malaria prevalence and contributed to an emergence of disease in New Zealand.

/pdf/ecology-and-conservation-biology-of-avian-malaria-4gop6ca3im.pdf

Ecology and conservation biology of avian malaria

Hawaiian honeycreepers (Aves: Drepanidinae) evolved in the absence of mosquito-borne diseases such as avian malaria (Plasmodium spp.). Malaria has been largely responsible for the recent wave of extinctions and endangerment among Hawaiian forest birds, which began by the 1920s. Most honeycreepers, especially endangered species, now persist only in forests above 1500 m elevation, where cool temperatures prevent effective malaria development in mosquitoes. We report here that prevalence of malaria in Hawaiian forest birds at 1900 m on the island of Hawai‘i has more than doubled over a decade. This increase was associated with breeding of mosquitoes and warmer summertime air temperatures. We also report direct evidence of tolerance to malaria, and a possible cost of tolerance, in wild native birds. Tolerance is adding to a reservoir of malaria at upper elevations even while vectors are rare and air temperatures are too low for complete development of the parasite in the vector. The data provide a gl...

Increase in avian malaria at upper elevation in hawai‘i

Background: The akepa population in its high-density site crashed in 2006, after being non-viable from 2000 to 2005. Hypothesis: The crash was caused by increases in certain ectoparsites and an introduced avian competitor. Organisms: Hawaii akepa (Loxops coccineus coccineus), Japanese white-eye (Zosterops japonicus), and Phthiraptera (chewing lice in Ischnocera and Amblycera). Field site: Hakalau Forest National Wildlife Refuge, Mauna Kea, Island of Hawaii, State of Hawaii, USA. Methods: We mist-netted birds at a high elevation site from 1987 to 2006, documenting increased numbers of introduced Japanese white-eye from 2000 to 2005, and compared Hawaii akepa nestling mass, breeding success, fledgling mass, juvenile survival, juvenile bill length, and sex ratio of young birds before and after the increase in white-eye. We inspected birds captured in mist-nets for ectoparasites. We identified colour-banded birds through binoculars to supplement the mist-netting for estimating population changes. Results: Declines in all demographic parameters of Hawaii akepa related to recruitment coincide with the first 5 years of increased numbers of Japanese white-eye. A severe decline in adult survival was observed in 2006, following the explosive increase in chewing lice between 2003 and 2005 and continued exposure to increased white-eyes. Further decline was observed in 2008. Mass, fault bars in feathers, fat scores, and changes in begging indicated that the decline was due to strong food limitation. The white-eye overlaps foraging substrates with all species of native birds, and additional native species have declined with the akepa. Conclusions: There has been a collapse of every demographic parameter of the akepa. The population is continuing to decline over a large area and may go extinct without

Incipient extinction of a major population of the Hawaii akepa owing to introduced species.

Ectoparasites, particularly chewing lice in the Phthiraptera (Insecta), affect the ecology of numerous host species. Most lice are highly host-specific, and there are no documented cases of major increases of chewing lice, within populations, over years. During continuous study from 1987-2005 at upper elevation forests on the island of Hawaii, chewing lice were exceedingly rare and, until 2003, were found in just 2 of 12 species of native and introduced birds. From 2003-2005, there was an explosive increase in the prevalence of chewing lice in all host species. There was no change in humidity, or in behavior of hosts, that could have caused an ecological release of existing lice. Based on reduced fat levels and increases in broken wing and tail feathers for most host species, there was apparently a food limitation that preceded the increase. The increase coincided temporally with detection of a nonnative bird that had recently been found in elevations below the study sites. Although there were isolated sightings of this bird on the study sites, seasonal movements and behavior of some species of native birds could also have allowed greater transmission to study sites. Both prevalence and intensity of infection, indexed by number of body regions parasitized, were lower in native species with greater bill overlap, a character that could help birds control lice. Seasonality of prevalence indicated that low prevalence preceded molt and high prevalence occurred after molting of hosts. The number of major fault bars in wing and tail feathers, a sign of nutritive stress, was correlated with intensity of infection, indicating an indirect cost to the hosts of being parasitized. In addition, birds with lice were less likely to be recaptured than birds without lice.

https://bioone.org/journals/journal-of-parasitology/volume-94/issue-5/GE-1378.1/Explosive-Increase-in-Ectoparasites-in-Hawaiian-Forest-Birds/10.1645/GE-1378.1.pdf

Gustav R. Bodner

Papers

Increase in avian malaria at upper elevation in hawai‘i

Incipient extinction of a major population of the Hawaii akepa owing to introduced species.

Explosive Increase in Ectoparasites in Hawaiian Forest Birds