by Allison Hu
Drought conditions in Amazonia are associated with increased fire incidence, enhancing aerosol emissions with degradation in air quality. On average, the Brazilian Amazon experiences extreme flood or drought once every ten years (Smith et al. 2014). However, in 2005 and 2010, only a five-year period, two mega droughts have occurred in the Amazon. Although the 2005 drought was the first in 100 years, the second drought occurred only five years later in 2010. Environmental impacts of drought include tree mortality from water deficits and social impacts include lack of food, lack of medical supplies, isolation of communities, and even health problems. Health issues arise because during droughts, wind erosion in deforested areas causes soil particles and microbes to be blow into the air, creating and exacerbating respiratory problems and triggering allergies. Furthermore, droughts have a positive correlation with fire incidences – in Amazonia, droughts can lead to over 30% increase in fire occurrence. This too leads to more hazardous health issues as smoke from fires tends to carry fine Particulate Matter particles (PM2.5), that when inhaled, may reach deep into the lungs, causing irritation of the throat, lungs, and eyes. The primary location for fires within the Amazon is centered around the southern and eastern periphery where 85% of fires occur, emitting as much as 300-600 mg/m3 of PM10 per 24 hours and up to 400 mg/ m3 of PM2.5 per 24 hours during the dry season (Smith et al.). Measurements carried out in southern Amazonia demonstrated that exposure to PM2.5 have positive associations with children’s respiratory health. This increase of 10 mg/m3 PM2.5 has shown simultaneous correlation with a 5.6% and 2.9% increase in outpatients in Rio Branco, Acre State, and Alta Floresta, Mato Grosso State, respectively.
Despite recent demonstrations of the impact of droughts and fire on tropical ecosystems, there is still a lack of large-scale assessments that inhibit testing of how these droughts would affect the tropical population’s health. Therefore, the availability of operational satellite-derived rainfall from the Tropical Rainfall Measuring Mission satellite (TRMM); active fires and aerosol from Terra/MODIS satellite; and deforestation rates from the National Institute for Space Research (INPE) datasets; together with the geo-spatial information about socio-economic indices from the Brazilian Institute of Geography and Statistics (IBGE) and hospitalizations from the Brazilian Health System (SUS), provide a unique opportunity to quantify the sensitivity of children’s respiratory health to environmental changes induced by recent droughts in the whole Brazilian Amazon (Smith et al.). By determining the relationships between respiratory health and recent Amazonian drought events, an approximation of the expected responses of health to future climate conditions can be provided. Thus, Smith et al. tested whether the incidence of respiratory diseases during two major droughts (2005 and 2010) was statistically dependent on drought-related environmental changes and socio-economic factors by using Geographically Weighted Poisson Regression models (GWPR) for the entire Brazilian Amazon.
In order to establish the extent and duration of the drought conditions, Smith et al. calculated rainfall, active fire, and aerosol anomalies as a departure from the 2001–2010 long-term mean. Data demonstrated that peak hospitalizations in Acre generally occur at the end of the wet season, however during the 2005 drought, this peak was displaced and in accordance with the fire season, indicating a direct effect. High concentrations of smoke were recorded in Rio Branco during September 2005, which could explain the local parameter estimate for aerosol in this region. (Human Development Index) HDI was significantly positive in drought-affected municipalities in Rondônia, western Mato Grosso, Pará, and Maranhão States, but not around the epicentre of the 2005 drought in Acre (Smith et al.).
Additionally, despite the 2010 drought being of greater magnitude than the 2005 drought, the impact on respiratory diseases was not as severe. The strength of HDI in 2010 in relation to the environmental variables may be due to the large spatial extent of the drought, which disguised localized environmental impacts, compared to 2005 when the drought was concentrated around Acre State. Therefore, drought events deteriorated children’s respiratory health particularly during 2005 when the drought was more geographically concentrated. Aerosol was significantly and positively related to respiratory disease incidence in southern Pará. However, along the eastern and southern edge of the region, aerosol loads do not increase the number of hospitalizations. This may be because the population living in these locations are accustomed to air pollution exposure as this area sees most fires occurring year on year. Furthermore, the 2010 drought experienced fewer fires and anomalous aerosol loads compared to 2005.
This is the first analysis of the impacts of drought on respiratory health of children under-five years at the scale of the whole Brazilian Amazon. Despite the wide trend of respiratory diseases peaking at the end of the wet season, drought condition exacerbates the incidence of respiratory diseases in children during the dry season. Aerosol, followed by HDI, was the primary driver of hospitalizations in drought-affected municipalities during 2005 (Smith et al.). Conversely, during the drought of 2010, HDI overcame the impact of aerosol, probably due to the decrease in aerosol emissions associated with a reduction of 1.9% in fire incidence in 2010 compared to 2005.
This study brings a new dimension into the debate around climate and environmental change impacts in tropical nations. It is now possible to conclude that in the Brazilian Amazon, not only are forests threatened by drought and fires, but also human populations exposed to health-hazardous agents. However, it is encouraging that by efficiently enforcing fire control legislation and curbing fire usage, policy makers could mitigate fire impacts on ecosystems and on human health (Smith et al.). Adaptation measurements are also necessary in terms of establishing hospitals in critical areas and planning for greater demand on health services during these crucial drought periods. These policies, together, have huge potential in ensuring better life quality for local populations and possibly improving and minimizing public expenditure for treatment and life costs during future drought events.
Smith, L. T., Aragão, L. E., Sabel, C. E., & Nakaya, T., 2014. Drought impacts on children’s respiratory health in the Brazilian Amazon. Scientific reports, 4.