Assessing the Impacts of Desert Afforestation on the Spread of Infectious Agents

Afforestation of the Sahara and Australian deserts has been proposed as a geoengineering technique by which to mitigate the effects of greenhouse gases in the Earth's atmosphere. The afforestation proposal entails planting and irrigating eucalyptus forests on a massive scale in the present-day arid Sahara desert-an expensive but potentially effective way to sequester atmospheric C02. Several unintended consequences have been associated with this technique, to include salt deposition, decreased oceanic fertilization by dust, and locust swarms. However, the effect of desert afforestation on the propagation of disease-carrying avian species has not been studied. It is hypothesized that afforestation of the Sahara will increase the number of avian species carrying disease to European and sub-Saharan regions. To assess this possibility, a field test scheme is presented to measure avian flux through the trans-Saharan region via radar-based monitoring. The test will assess flux for both arid and afforested conditions at several points along major trans-Saharan flyways, with emphasis on zones known to be fatal for Sahara-crossing birds. Results from the field experiments will be input into an in silico model that will extrapolate the findings over the entire Sahara region and incorporate other parameters such as breeding. The preliminary model described here will simulate flux of disease-carrying avian species across the Sahara for a user-defined number of migratory seasons, and will compare changes in species-specific flux, migratory patterns, and cross-infection between arid and afforested scenarios. It is expected that desert afforestation will heighten trans-Saharan flux of disease-carrying avian species. If this prediction is validated by the simulation, then European and sub-Saharan regions may be at greater risk of avian-borne disease if Sahara afforestation is implemented. Desert afforestation as a geoengineering technique must be critically assessed with respect to its potential effects on disease vector propagation before its implementation is considered. The proposed experiments provide an outline with which to effectively estimate such effects, should the need for long-term risk assessment arise.