Wind can connect a desert to a forest. From CALIPSO observations for 2007–2013, the studies estimate about 182 million tonnes of dust a year passing the western coast of North Africa and 27.7 million deposited in the Amazon basin. The second flow is part of the first: do not add the bars together. [1][2][3]
These are historical estimated averages, with large uncertainties: the Amazon study gives a range of around 8–48 million tonnes per year. Dust also carries phosphorus, a nutrient; these figures do not show that the forest is protected against present pressures. [3]