In the article the claim is that the environment changes due to the presence of the forest and results in more precipitation.
i.e. the presence of precipitation and trees are linked. If you remove one you remove the other, and if you add one (trees in this case) you get the other.
>But for the past 2,000 years or so, the climate of the Sahara has been fairly stable. The northeastern winds dry out the air over the desert and drive hot winds toward the equator. These winds can reach exceptional speeds and cause severe dust storms that can drop local visibility to zero. Dust from the Sahara travels on trade winds all the way to the opposite side of the globe.
>Precipitation in the Sahara ranges from zero to about 3 inches of rain per year, with some locations not seeing rain for several years at a time. Occasionally, snow falls at higher elevations. Daytime summer temperatures are often over 100 degrees Fahrenheit (38 degrees Celsius) and can drop to near-freezing temperatures at nighttime.
Precipitation is controlled by the humidity in the prevailing wind systems. Prevailing winds from the northeast drop whatever moisture they have on the southern margins of the Mediterranean or on Egypt and Sudan.
i.e. the presence of precipitation and trees are linked. If you remove one you remove the other, and if you add one (trees in this case) you get the other.
Pretty amazing if true.