This was excessive deforestation due to the pressures of the debt. Which led to desertification. This excessive deforestation didn't happen in the Dominican Republic, which explains the difference. If you visit Haiti and the Dominican Republic you would be able to tell the difference in climate and soil.
"To the west of the island of Hispaniola is Haiti, only 3% of which now has forest coverage. Although the
Dominican Republic that makes up the east of the island still has 23%. At least 90% of Haiti’s soils have been
severely degraded by deforestation and inappropriate cultivation as compared to 40% for the Dominican Republic." [1]
Not sure if desertification is the right word for "all the fertile topsoil washed off the hills in the rains, and without trees to moderate drainage, river flood more often, and those floods cover productive land downstream in infertile silt".
Those things aren't mutually exclusive. Did you take from what I said to mean that the entire country turned into a desert?
Haiti has become more desertic in some parts due to the deforestation and that causes a number of things to happen that affect soil quality including floods.
"To the west of the island of Hispaniola is Haiti, only 3% of which now has forest coverage. Although the Dominican Republic that makes up the east of the island still has 23%. At least 90% of Haiti’s soils have been severely degraded by deforestation and inappropriate cultivation as compared to 40% for the Dominican Republic." [1]
[1] - https://www.researchgate.net/publication/269670285_A_Case_St...