El cambio climático, la salud humana y el desarrollo sostenible / Climate change, human health, and sustainable development

El cambio climático debido a actividades humanas pone en peligro los ecosistemas y la salud humana a escala mundial. Con el fin de hacer frente a las amenazas que se ciernen sobre los ecosistemas en todo el mundo, en el decenio de 1980 se introdujo el concepto del desarrollo sostenible. Desde entonces, ese concepto se ha aplicado ampliamente para guiar y enfocar la formulación de políticas. En el presente artículo se examinan las consecuencias sanitarias que tiene el cambio climático debido a actividades humanas para el desarrollo sostenible, en particular su posible efecto en el abastecimiento de alimentos, los desastres naturales, las enfermedades infecciosas, los ecosistemas y la elevación del nivel del mar. Se discute un modelo integrado que contiene los principales indicadores del desarrollo sostenible. También se examina la importancia que tienen el cambio climático, la salud humana y el desarrollo sostenible para las políticas internacionales pertinentes.

Human-induced climate change threatens ecosystems and human health on a global scale. In order to withstand the worldwide threats to ecosystems, the concept of sustainable development was introduced during the 1980s. Since then, this concept has been widely applied to guide and focus policy-making. The present article reviews the health consequences of human-induced climate change on sustainable development, particularly the potential impact of such change on food supply, natural disasters, infectious diseases, ecosystems, and sea level rise. Discussed is an integrated model containing the key indicators of sustainable development. The relevance of climate change, human health, and sustainable development for international climate change policy is also examined.

Malaria in the African highlands: past, present and future.

Many of the first European settlers in Africa sought refuge from the heat and diseases of the plains by moving to the cool and salubrious highlands. Although many of the highlands were originally malaria free, there has been a progressive rise in the incidence of the disease over the last 50 years, largely as a consequence of agroforestry development, and it has been exacerbated by scarce health resources. In these areas of fringe transmission where the malaria pattern is unstable, epidemics may be precipitated by relatively subtle climatic changes. Since there is little immunity against the disease in these communities, outbreaks can be devastating, resulting in a substantial increase in morbidity and death among both children and adults. We present here the results obtained using a mathematical model designed to identify these epidemic-prone regions in the African highlands and the differences expected to occur as a result of projected global climate change. These highlands should be recognized as an area of special concern. We further recommend that a regional modelling approach should be adopted to assess the extent and severity of this problem and help improve disease surveillance and the quality of health care delivered in this unstable ecosystem.

PIP: This article explores the past, present and future trends of malaria in the African highlands. Over the last 50 years, there has been a progressive increase in the incidence of malaria in the region, particularly in the highlands. This trend is brought primarily as a consequence of agroforestry development and the scarcity of health resources. In these areas of fringe transmission where malaria pattern is unstable, outbreaks may be precipitated by certain climate and biological factors that favors the growth and development of mosquito vector and parasite. Since there is little immunity against the disease in these communities, epidemics can be devastating, resulting in a significant rise in morbidity and mortality among children and adults. This paper outlines the results using a mathematical model designed to determine epidemic-prone regions in the African highlands and the differences that are expected to occur as a product of projected global climate change. These communities should be recognized as an area of special attention. A regional modeling approach is recommended to examine the extent of severity of the problem and to improve disease surveillance and the quality of health care services.

Health impacts of climate change and ozone depletion: an ecoepidemiologic modeling approach.

Anthropogenic climate changes and stratospheric ozone depletion affect human health in various ways. Current mainstream epidemiologic research methods do not appear well adapted to analyze these health impacts, which involve complex systems influenced by human interventions or simpler processes that will take place in the future. This paper discusses a different paradigm for studying the health impacts of global environmental changes and focuses on the development of integrated ecoepidemiologic models using three examples--the effect of climate change on vector-borne diseases, the effect of climate change on thermal-related mortality, and the effects of increasing ultraviolet levels because of ozone depletion on the rates of skin cancer.

Climate change, thermal stress and mortality changes.

One of the potential effects of an anthropogenically induced climate change is a change in mortality related to thermal stress. In this paper, existing literature on the relationship between average temperatures and mortality is evaluated. By means of a simple meta-analysis an aggregated effect of a change in temperature on mortality is estimated for total, cardiovascular and respiratory mortality. These effect estimates are combined with projections of changes in baseline climate conditions of 20 cities, according to climate change scenarios of three General Circulation Models (GCMs). The results indicate that for most of the cities included, global climate change is likely to lead to a reduction in mortality rates due to decreasing winter mortality. This effect is most pronounced for cardiovascular mortality in elderly people in cities which experience temperate or cold climates at present. The sensitivity of the results to physiological and socio-economical adaptation is examined. However, more research is necessary to extend this work by inclusion of data from a wider range of populations.

Dengue fever epidemic potential as projected by general circulation models of global climate change.

Climate factors influence the transmission of dengue fever, the world's most widespread vector-borne virus. We examined the potential added risk posed by global climate change on dengue transmission using computer-based simulation analysis to link temperature output from three climate general circulation models (GCMs) to a dengue vectorial capacity equation. Our outcome measure, epidemic potential, is the reciprocal of the critical mosquito density threshold of the vectorial capacity equation. An increase in epidemic potential indicates that a smaller number of mosquitoes can maintain a state of endemicity of disease where dengue virus is introduced. Baseline climate data for comparison are from 1931 to 1980. Among the three GCMs, the average projected temperature elevation was 1.16 degrees C, expected by the year 2050. All three GCMs projected a temperature-related increase in potential seasonal transmission in five selected cities, as well as an increase in global epidemic potential, with the largest area change occurring in temperate regions. For regions already at risk, the aggregate epidemic potential across the three scenarios rose on average between 31 and 47% (range, 24-74%). If climate change occurs, as many climatologists believe, this will increase the epidemic potential of dengue-carrying mosquitoes, given viral introduction and susceptible human populations. Our risk assessment suggests that increased incidence may first occur in regions bordering endemic zones in latitude or altitude. Endemic locations may be at higher risk from hemorrhagic dengue if transmission intensity increases.

Modeling malaria as a complex adaptive system.

As the resistance of the malaria parasite to antimalarial drugs continues to increase, as does that of the malarial mosquito to insecticides, the efficacy of efforts to control malaria in many tropical countries is diminishing. This trend, together with the projected consequences of climate change, may prove to exacerbate substantially the significance of malaria in the coming decades. In this article we introduce the use of an evolutionary modeling approach to simulate the adaptation of mosquitoes and parasites to the available pesticides and drugs. By coupling genetic algorithms with a dynamic malaria-epidemiological model, we derive a complex adaptive system capable of simulating adapting and evolving processes within both the mosquito and the parasite populations. This approach is used to analyze malaria management strategies appropriate to regions of higher and lower degrees of endemicity. The results suggest that adequate use of insecticides and drugs may reduce the occurrence of malaria in regions of low endemicity, although increased efforts would be necessary in the event of a climate change. However, our model indicates that in regions of high endemicity the use of insecticides and drugs may lead to an increase in incidence due to enhanced resistance development. Projected climate change, on the other hand, may lead to a limited reduction of the occurrence of malaria due to the presence of a higher percentage of immune persons in the older age class.

Climate change, human health, and sustainable development.

Human-induced climate change threatens ecosystems and human health on a global scale. In order to withstand the worldwide threats to ecosystems, the concept of sustainable development was introduced during the 1980s. Since then, this concept has been widely applied to guide and focus policy-making. The present article reviews the health consequences of human-induced climate change on sustainable development, particularly the potential impact of such change of food supply, natural disasters, infectious diseases, ecosystems, and sea level rise. Discussed is an integrated model containing the key indicators of sustainable development. The relevance of climate change, human health, and sustainable development for international climate change policy is also examined.

Model stimulations to estimate malaria risk under climate change.

The current geographic range of malaria is much smaller than its potential range. In many regions there exists a phenomena characterized as "Anophelism without malaria." The vectors are present but malaria transmission does not occur. Vectorial capacity often has been used as a parameter to estimate the susceptibility of an area to malaria. Model computations with global climatological data show that a dynamic concept of vectorial capacity can be used as a comparative risk indicator to predict the current extent and distribution of malarious regions in the world. A sensitivity analysis done in 3 distinct geographic areas shows that the areas of largest change of epidemic potential caused by a temperature increase are those where mosquitoes already occur but where development of the parasite is limited by temperature. Computations with the model presented here predict, with different climate scenarios, an increased malaria risk in areas bordering malaria endemic regions and at higher altitudes within malarious regions under a temperature increase of 2-4 degrees C.

Climate change and malaria: exploring the risks.

That the enhanced greenhouse effect may prove to influence human health will come as no surprise. One of the potential health consequences is a change in distribution patterns of vector-borne diseases. In tropical countries, such diseases are a major cause of illness and death. One of the most important vector-borne diseases in the world is malaria, which is associated with one of four species of parasite and transmitted by a mosquito vector. Climatic conditions, and temperature in particular, directly influence mosquito development, feeding-frequency and longevity of the mosquito, as well as the time in which the parasite develops inside the mosquito. Other environmental factors such as vegetation and breeding sites are indirectly influenced by climate conditions. In order to assess the impact of an anthropogenic climate change on the transmission of malaria, an integrated assessment model has been developed. In this integrated model, the direct effects of a change in temperature and precipitation on the transmission potential of a mosquito population is assessed by means of the vectorial capacity. The effect of a human-induced climate change on human health is evaluated by assessing the change in malaria prevalence and disease burden. A sustainable development index, which is an aggregate of an environmental pressure indicator, a health indicator and a socio-economic development indicator is introduced and discussed. Such an index can be used to determine whether future projections are sustainable.

Potential impact of global climate change on malaria risk.

The biological activity and geographic distribution of the malarial parasite and its vector are sensitive to climatic influences, especially temperature and precipitation. We have incorporated General Circulation Model-based scenarios of anthropogenic global climate change in an integrated linked-system model for predicting changes in malaria epidemic potential in the next century. The concept of the disability-adjusted life years is included to arrive at a single measure of the effect of anthropogenic climate change on the health impact of malaria. Assessment of the potential impact of global climate change on the incidence of malaria suggests a widespread increase of risk due to expansion of the areas suitable for malaria transmission. This predicted increase is most pronounced at the borders of endemic malaria areas and at higher altitudes within malarial areas. The incidence of infection is sensitive to climate changes in areas of Southeast Asia, South America, and parts of Africa where the disease is less endemic; in these regions the numbers of years of healthy life lost may increase significantly. However, the simulated changes in malaria risk must be interpreted on the basis of local environmental conditions, the effects of socioeconomic developments, and malaria control programs or capabilities.