Rosalie Woodruff

Climate change and human health: present and future risks

There is near unanimous scientific consensus that greenhouse gas emissions generated by human activity will change Earths climate. The recent (globally averaged) warming by 0.5 degrees C is partly attributable to such anthropogenic emissions. Climate change will affect human health in many ways-mostly adversely. Here, we summarise the epidemiological evidence of how climate variations and trends affect various health outcomes. We assess the little evidence there is that recent global warming has already affected some health outcomes. We review the published estimates of future health effects of climate change over coming decades. Research so far has mostly focused on thermal stress, extreme weather events, and infectious diseases, with some attention to estimates of future regional food yields and hunger prevalence. An emerging broader approach addresses a wider spectrum of health risks due to the social, demographic, and economic disruptions of climate change. Evidence and anticipation of adverse health effects will strengthen the case for pre-emptive policies, and will also guide priorities for planned adaptive strategies.

Comparative risk assessment of the burden of disease from climate change.

The World Health Organization has developed standardized comparative risk assessment methods for estimating aggregate disease burdens attributable to different risk factors. These have been applied to existing and new models for a range of climate-sensitive diseases in order to estimate the effect of global climate change on current disease burdens and likely proportional changes in the future. The comparative risk assessment approach has been used to assess the health consequences of climate change worldwide, to inform decisions on mitigating greenhouse gas emissions, and in a regional assessment of the Oceania region in the Pacific Ocean to provide more location-specific information relevant to local mitigation and adaptation decisions. The approach places climate change within the same criteria for epidemiologic assessment as other health risks and accounts for the size of the burden of climate-sensitive diseases rather than just proportional change, which highlights the importance of small proportional changes in diseases such as diarrhea and malnutrition that cause a large burden. These exercises help clarify important knowledge gaps such as a relatively poor understanding of the role of nonclimatic factors (socioeconomic and other) that may modify future climatic influences and a lack of empiric evidence and methods for quantifying more complex climate–health relationships, which consequently are often excluded from consideration. These exercises highlight the need for risk assessment frameworks that make the best use of traditional epidemiologic methods and that also fully consider the specific characteristics of climate change. These include the long-term and uncertain nature of the exposure and the effects on multiple physical and biotic systems that have the potential for diverse and widespread effects, including high-impact events.

Predicting Ross River Virus Epidemics from Regional Weather Data

Background. Diseases caused by arboviruses cause extensive mortality and morbidity throughout the world. Weather directly affects the breeding, abundance, and survival of mosquitoes, the principal vector of many arboviruses. The goal of this study was to test whether climate variables could predict with high levels of accuracy (more than 70%) epidemics of one arbovirus, Ross River virus disease. Methods. Weather data from two regions in southeastern Australia were matched with Ross River virus disease data for the period 1991 to 1999. Our aim was to develop simple models for the probability of the occurrence of an epidemic in an area in a given year. Results. Two predictable epidemic patterns emerged, after either high summer rainfalls or high winter rainfalls. A prerequisite relating to host-virus dynamics was lower than average spring rainfall in the preepidemic year. The sensitivity of the model was 96% for Region 1 and 73% for Region 2. Conclusions. Early warning of weather conditions conducive to outbreaks of Ross River virus disease is possible at the regional level with a high degree of accuracy. Our models may have application as a decision tool for health authorities to use in risk-management planning.

Health Impact Assessment of Global Climate Change: Expanding on Comparative Risk Assessment Approaches for Policy Making

Climate change is projected to have adverse impacts on public health. Cobenefits may be possible from more upstream mitigation of greenhouse gases causing climate change. To help measure such cobenefits alongside averted disease-specific risks, a health impact assessment (HIA) framework can more comprehensively serve as a decision support tool. HIA also considers health equity, clearly part of the climate change problem. New choices for energy must be made carefully considering such effects as additional pressure on the worlds forests through large-scale expansion of soybean and oil palm plantations, leading to forest clearing, biodiversity loss and disease emergence, expulsion of subsistence farmers, and potential increases in food prices and emissions of carbon dioxide to the atmosphere. Investigators must consider the full range of policy options, supported by more comprehensive, flexible, and transparent assessment methods.

Detecting the Health Effects of Environmental Change: Scientific and Political Challenge

Scientists fluent in ecology and the earth sciences understand that the current scale of human-induced changes to the biosphere entails risks of systemic dysfunction. Ecosystem processes, being complex and often nonlinear, are somewhat unpredictable in their responses to major external stressors (Egler, 1986; Levin, 1999; Gunderson and Holling, 2002). These issues are not yet prominent or well understood within population health research circles. Yet it is a reasonable expectation that this ongoing impairment of Earth’s life-support functions poses substantial risks to human health. It is axiomatic that humans rely on functioning ecosystems (potable water, breathable air, arable land, and food-producing ecosystems) for survival. Substantial evidence, including that from high-resolution paleoclimatic data, shows the link between abrupt climate changes (typically aridity) and the collapse of ancient societies (Weiss and Bradley, 2001). Severe and prolonged droughts forced the abandonment of agricultural settlements and the collapse of the Akkadian empire in Syria just before 2200 BC (Lemcke and Sturm, 1997; Cullen et al., 2000) and the collapse of the classic Mayan civilization in Mesoamerica in the ninth century AD (Brenner et al., 2001). Beyond these extreme examples, however, we have very little detailed knowledge about how changes to ecosystem functioning affect human health and well-being. The work of the Intergovernmental Panel on Climate Change has not yet identified certain evidence of effects on human health attributable to climate change (McMichael and Githeko, 2001). Similarly, the nearly completed Millennium (Ecosystem) Assessment project has documented very few clear examples of adverse effects on human health due to human-induced ecosystem changes. This situation is both scientifically tantalizing and politically important. For example, consider the political aspect. We are dealing with complex, and not yet widely understood, changes in large biogeophysical systems. Models can be used to estimate future human biological and social impacts on the assumption, for example, that current trends in global climate change will continue. However, for many policy makers (confined within more immediate electorally defined time horizons), such futuredisplaced forecasts of adverse consequences may lack relevance. To make the topic tangible and substantial, we should strive to link currently observable adverse health effects of environmental changes with the likely future effects of large-scale biogeophysical environmental changes impinging on whole populations. Then, if we can communicate how the well-being and health of human populations is jeopardized by these global environmental changes, we will illuminate society’s understanding of the essentials of sustainability. As researchers, various scientific issues tantalize us. First, effects on human health emerge only gradually (in human experiential terms), because changes to system functioning and to the pattern of environmental events occur over decadal time. The early evidence of health effects, in general, is therefore rather marginal. Second, most human health outcomes are multifactorial in their causation. A movement of highland malaria to higher altitudes could result from land-use change, population movement (including from the more malarious lowlands), changes in pesticide programs, and regional climatic changes (Hales and Woodward, 2003; Reiter et al., 2004). Apportioning causal influence among such coexistent—and often interacting—factors is difficult. EcoHealth 2, 1–3, 2005 DOI: 10.1007/s10393-004-0152-0

Early Warning of Ross River Virus Epidemics: Combining Surveillance Data on Climate and Mosquitoes

Background: Ross River virus disease is spread by mosquitoes, and an average of 5000 people are infected each year in Australia. It is one of the few infectious diseases for which climate-based early warning systems could be developed. The aim of this study was to test whether supplementing routinely collected climate data with mosquito surveillance data could increase the accuracy of disease prediction models. Methods: We focused on a temperate region of Western Australia between July 1991 and June 1999. We developed “early” and “later” warning logistic regression models to test the sensitivity of data on climate (tide height, rainfall, sea surface temperature) and mosquito counts for predicting epidemics of disease. Results: Climate data on their own were moderately sensitive (64%) for predicting epidemics during the early warning period. Addition of mosquito surveillance data increased the sensitivity of the early warning model to 90%. The later warning model had a sensitivity of 85%. Conclusions: We found that climate data are inexpensive and easy to collect and allow the prediction of Ross River virus disease epidemics within the time necessary to improve the effectiveness of public health responses. Mosquito surveillance data provide a more expensive early warning but add substantial predictive value.

Climate Change-related Health Impacts in the Hindu Kush–Himalayas

Our goal was to identify the climate change-related health risks and vulnerable populations specific to the mountainous regions of the Hindu Kush–Himalayas. We reviewed published information of the likely health consequences of climate change in mountain regions, especially the findings of a workshop for countries in the Hindu Kush–Himalaya region, organized by the World Health Organization, World Meteorological Organization, United Nations Environment Programme, and United Nations Development Programme. The main climate-related risks in the Hindu Kush–Himalaya region include the expansion of vector-borne diseases as pathogens take advantage of new habitats in altitudes that were formerly unsuitable. Diarrheal diseases could become more prevalent with changes in freshwater quality and availability. More extreme rainfall events are likely to increase the number of floods and landslides with consequent death and injuries. A unique risk is sudden floods from high glacier lakes, which cause substantial destruction and loss of life. Because glaciers are the main source of freshwater for upland regions and downstream countries, the long-term reduction in annual glacier snowmelt is expected to heighten existing water insecurity in these areas. Climate change also is bringing some benefits to mountain populations, including milder winters and longer growing seasons. Populations in mountain regions have unique combinations of vulnerabilities to climate change. The extent of the health impacts experienced will depend on the effectiveness of public health efforts to identify and implement low-cost preparedness and response measures, and on the speed at which emissions of greenhouse gas emissions can be reduced.

Action on climate change: the health risks of procrastinating

Objective: The worlds climate will continue to change because of human influence. This is expected to affect health, mostly adversely. We need to compare the projected health effects in Australia arising from differing climate change scenarios to inform greenhouse gas emission (mitigation) policy.

Climate Change and Infectious Disease

Publisher Summary The worldwide upturn in the occurrence of both new (emerging) and reemerging or spreading infectious diseases highlights the importance of underlying environmental and social conditions as determinants of the generation, spread, and impact of infectious diseases in human populations. Human ecology is undergoing rapid transition. This encompasses urbanization, rising consumerism, changes in working conditions, population aging, marked increases in mobility, changes in culture and behavior, evolving health-care technologies, and other factors. Global climate change is becoming a further, and major, large-scale influence on the pattern of infectious disease transmission. It is likely to become increasingly important over at least the next halfcentury, as the massive, highinertial, and somewhat unpredictable process of climate change continues. The many ways in which climate change does and will influence infectious diseases are subject to a plethora of modifying influences by other factors and processes: constitutional characteristics of hosts, vectors and pathogens; the prevailing ambient conditions; and coexistent changes in other social, economic, behavioral, and environmental factors. This global anthropogenic process, climate change, along with other unprecedented global environmental changes, is beginning to destabilize and weaken the planets life-support systems. Infectious diseases, unlike other diseases, depend on the biology and behavior—each often climate-sensitive—of two or more parties. Hence, these diseases will be particularly susceptible to changes as the worlds climate and its climate-sensitive geochemical and ecological systems undergo change over the coming decades.

Climate change could threaten blood supply by altering the distribution of vector-borne disease: an Australian case-study

Background: Climate change is expected to promote more intense and prolonged outbreaks of vector-borne disease, and alter the geographic boundaries of transmission. This has implications for the safety and supply of fresh blood products around the world. In Australia, a recent outbreak of dengue fever caused a prolonged regional shortage in the supply of fresh blood products. Objective: To highlight the potential for climate change to affect the safety and supply of blood globally through its impact on vector-borne disease, using the example of dengue in Australia as a case-study. Design: We modelled geographic regions in Australia suitable for dengue transmission over the coming century under four climate change scenarios, estimated changes to the population at risk and effect on blood supply. Results: Geographic regions with climates that are favourable to dengue transmission could expand to include large population centres in a number of currently dengue-free regions in Australia and reduce blood supply across several states. Conclusion: Unless there is strong intergovernmental action on greenhouse gas reduction, there could be an eight-fold increase in the number of people living in dengue prone regions in Australia by the end of the century. Similar impacts will be experienced elsewhere and for other vector-borne diseases, with regions currently on the margins of transmission zones most affected. Globally, climate change is likely to compound existing problems of blood safety and supply in already endemic areas and cause future shortages in fresh blood products through its impact on transmission of vector-borne disease.