Reports from Haiti say that tropical storm Jeanne has caused over 1,000 deaths, mainly in the north-west.
By Richard Black
BBC science correspondent
The interim Prime Minister Gerard Latortue says that tens of thousands more are without food and water.
Haiti is one of the most deforested nations on Earth
It's the latest in a long line of natural disasters for the impoverished Caribbean state.
Environmental destruction and lack of economic development are major factors behind the trend.
Haiti is one of the poorest, most densely populated and most deforested countries on Earth.
These three factors are all interlinked, in a vicious circle which makes Haiti particularly vulnerable to storms like Jeanne.
Poverty means that people take what they can from the land - in this case, wood, either burnt locally or converted into charcoal for use in the cities.
Because there are so many people - around eight million - there is more deforestation - a United Nations report ten years ago said that forest cover was 'impaired' in 97% of the country.
Without tree roots to bind soil together, it's simply washed away by heavy rain.
After the flood, there is even less land to use - resulting in yet more poverty.
Normal rainfall slowly removes soil underneath houses, meaning that a flash flood will tear them away in seconds.
In May this year, heavy rains and floods caused another 500 deaths.
Then and now, the neighbouring Dominican Republic fared much better, largely because living standards are much higher.
None of this is news to development agencies working in Haiti - but what they can do about it, given the country's turbulent history, the vast disparities between rich and poor, and the scale of environmental destruction, is another matter.