Infectious diseases can cause rapid population declines or species extinctions. Many pathogens of terrestrial and marine taxa are sensitive to temperature, rainfall, and humidity, creating synergisms that could affect biodiversity. Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Although most host-parasite systems are predicted to experience more frequent or severe disease impacts with warming, a subset of pathogens might decline

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Climate Warming and Disease Risks for Terrestrial and Marine Biota

The world’s coral reefs are being degraded, and the need to reduce local pressures to offset the effects of increasing global pressures is now widely recognized. This study investigates the spatial and temporal dynamics of coral cover, identifies the main drivers of coral mortality, and quantifies the rates of potential recovery of the Great Barrier Reef. Based on the world’s most extensive time series data on reef condition (2,258 surveys of 214 reefs over 1985–2012), we show a major decline in coral cover from 28.0% to 13.8% (0.53% y−1), a loss of 50.7% of initial coral cover. Tropical cyclones, coral predation by crown-of-thorns starfish (COTS), and coral bleaching accounted for 48%, 42%, and 10% of the respective estimated losses, amounting to 3.38% y−1 mortality rate. Importantly, the relatively pristine northern region showed no overall decline. The estimated rate of increase in coral cover in the absence of cyclones, COTS, and bleaching was 2.85% y−1, demonstrating substantial capacity for recovery of reefs. In the absence of COTS, coral cover would increase at 0.89% y−1, despite ongoing losses due to cyclones and bleaching. Thus, reducing COTS populations, by improving water quality and developing alternative control measures, could prevent further coral decline and improve the outlook for the Great Barrier Reef. Such strategies can, however, only be successful if climatic conditions are stabilized, as losses due to bleaching and cyclones will otherwise increase.

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The 27–year decline of coral cover on the Great Barrier Reef and its causes

Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia's Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef-building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (>50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.

http://eprints.jcu.edu.au/1428/1/Bruno_et_al_2007_Thermal_stress_coral_cover_and_disease_PLos.pdf

Thermal Stress and Coral Cover as Drivers of Coral Disease Outbreaks

http://irceb.asu.edu/amphibians/text/actatrop.pdf

Anthropogenic environmental change and the emergence of infectious diseases in wildlife.

By using the criteria that define emerging infectious diseases (EIDs) of humans, we can identify a similar group of EIDs in wildlife. In the current review we highlight an important series of wildlife EIDs: amphibian chytridiomycosis; diseases of marine invertebrates and vertebrates and two recently-emerged viral zoonoses, Nipah virus disease and West Nile virus disease. These exemplify the varied etiology, pathogenesis, zoonotic potential and ecological impact of wildlife EIDs. Strikingly similar underlying factors drive disease emergence in both human and wildlife populations. These are predominantly ecological and almost entirely the product of human environmental change. The implications of wildlife EIDs are twofold: emerging wildlife diseases cause direct and indirect loss of biodiversity and add to the threat of zoonotic disease emergence. Since human environmental changes are largely responsible for their emergence, the threats wildlife EIDs pose to biodiversity and human health represent yet another consequence of anthropogenic influence on ecosystems. We identify key areas where existing expertise in ecology, conservation biology, wildlife biology, veterinary medicine and the impact of environmental change would augment programs to investigate emerging diseases of humans, and we comment on the need for greater medical and microbiological input into the study of wildlife diseases. © 2001 Elsevier Science B.V. All rights reserved.

Review article Anthropogenic environmental change and the emergence of infectious diseases in wildlife

Reefs in the Florida Keys are experiencing a dramatic increase in the number of localities and number of species with coral disease. In extensive surveys from Key Largo to Key West in 160 stations at 40 randomly chosen sites, there has been a dramatic increase in (1) the number of locations exhibiting disease (82% of all stations are now affected, a 404% increase over 1996 values), (2) the number of species affected (85% of all species are now affected, a 218% increase over 1996 values), and (3) the rate of coral mortality (the deep fore-reef at Carysfort experienced a 60% reduction of living coral cover during the survey). Two null hypotheses (1) that the incidence of disease has remained constant through time and (2) that the apparent increase in disease is due to a lack of comparable earlier data, are both falsified. Different diseases exhibit different patterns of spread: some diseases (e.g. black band) exhibit low incidence and jump rapidly between sites; other diseases (e.g. white pox) exhibit patchy distributions and increase in frequency at affected sites from one year to the next. The central question of why so many corals are becoming simultaneously susceptible to a host of marine pathogens remains unanswered.

Vladimir Kosmynin

Papers

Patterns of spread of coral disease in the Florida Keys

Patterns of spread of coral disease in the Florida Keys. Hydrobiologia