11 November 2010

Deforestation, erosion and Cholera in Haiti

Posted by Dave Petley

There is an interesting and provocative recent article on the Huffington Post website by Ethan Budiansky, who works for an NGO called Trees for the Future, which seeks to assist communities and farmers in less developed countries to plant woodlands in order to mitigate environmental damage. The article looks at the issue of deforestation in Haiti, and attempts to link the ongoing cholera outbreak across the country to the rampant deforestation there. That deforestation is an issue in Haiti is beyond doubt – indeed I have blogged on this previously. I am certainly not the first to note that the border between the Dominican Republic (to the east and north in the Google Earth image below) and Haiti (to the south and west – the white line is the approximate location of the border) is visible from the air purely on the basis of the remarkable change in forest density:

The reasons for the forest loss to this extent are of course complex, but include the extreme levels of poverty in what has been to all intents and purposes a failed state, in which fuel security and management of resources (i.e. prevention of uncontrolled logging) have both been deeply problematic.  Note from the image above that in general the land has not been converted to agricultural use, and hence is not being managed.  This is of course a tropical environment with high rainfall intensities, and indeed tropical cyclones, meaning that erosion is inevitably a major issue.

The article argues that deforestation may be one of the causes of the cholera outbreak.  The thesis has a number of dimensions, all stemming from the loss of forest.  This forest loss leads to a decline in biodiversity and hence to poor quality soils, which are then susceptible to erosion during rainfall.   Apart from causing landslides, this erosion pollutes the water courses and prevents the production of food, leading to a vulnerable population.  The clogging of the water courses is also important as this allows the formation of pools of water that rapidly become stagnant and thus dangerous.  Meanwhile, the population has to rely on the rivers for the supply of  water, meaning that they are immediately exposed to disease.

The combination of people with a low level of resilience to disease and a polluted and clogged water delivery system, and I suspect a population that has to cope with regular mudslides, leads to increased likelihood of Cholera, with lethal effects.  Inevitably the proposed solution is to plant more trees.  Of course this is not a short term fix.  Indeed it will not mitigate the current outbreak of Cholera, or even outbreaks in the next few years.  However, the idea is that in the medium to long term afforestation will start to play role in mitigating the risks.

Whilst I find some of the arguments and technical details a little unclear (I wonder whether there is real evidence that the erosion is creating pools of water in the water courses in this way, and I wonder whether trees really raise the watertable through the action of their roots for example), the idea is certainly interesting and provocative.  The underlying message is certainly correct – i.e. that reforestation must be a key component of the rehabilitation of Haiti, but this can only be successful if the civil measures are in place that prevent unsustainable use of the forests.  This is going to be a long haul.