Dryland Salinity and Human Health Outcomes

Abstract

P-527 Large tracts of the Western Australian agricultural zone have become saline due to extensive land clearing for agriculture. Native perennial vegetation is replaced with shallow rooted crops and pastures resulting in rising water tables which dissolve salt in the soil layer and bring it to the surface. Currently it is calculated that approximately 5.7 million hectares are at risk or are affected by dryland salinity and models predict the situation worsening in the next 50 years. This environmental degradation has profound ecological impacts through the reduction of an already depleted biodiversity. Such ecosystem disruption has many adverse outcomes including an increased health risk among the resident human population. The current study takes an interdisciplinary, tiered approach using both epidemiological and ecological techniques. Environmental data was examined with human health data from Western Australia's Data Linkage Unit using spatial Bayesian modelling to determine if any associations exist between environmental degradation and the health of the human population. Mosquito-borne disease was chosen as a case study to investigate in detail as this has a complex disease ecology that is strongly influenced by environmental factors. Notifications of the primary mosquito-borne disease of concern in southern Australia, Ross River virus (RRV), were combined with environmental data, field sampling of mosquito populations and investigations of underlying trophic processes that regulate the ecology of the disease (such as predator-prey relationships between aquatic invertebrates and mosquitoes). This multi-disciplinary approach was used to investigate the impact of dryland salinity on mosquito-borne disease risk. The Bayesian modelling of ecosystem and human health found that increased rates of asthma, depression, suicide and ischemic heart disease were all positively associated with areas of increased dryland salinity. In the mosquito-borne disease case study, preliminary results indicate that dryland salinity has impacts on disease ecology and creates the potential for increased health risk. Populations of the main vector species of RRV in Australia were significantly higher in saline affected areas. For larval mosquitoes this relationship with salinity also correlated with a reduction in aquatic predators. This study represents the first attempt to investigate the impact between dryland salinity, the primary cause of ecosystem disruption in Australia, and human health outcomes. The findings clearly underline the link between environmental degradation and adverse human health outcomes; which may be further enhanced in the future given the predicted increase in extent and severity of dryland salinity over the next 50 years.