Trees / forests literally make their own rain.
(2015) https://theecologist.org/2015/mar/02/without-its-rainforest-...
Mainstream climatologists predict a 15% fall in rainfall over the Amazon if it is stripped of its rainforest. But the 'biotic pump' theory, rooted in conventional physics and recently confirmed by experiment, shows that the interior of a forest-free Amazon will be as dry as the Negev desert
(2019) https://www.theguardian.com/environment/2019/oct/23/amazon-r...
Soaring deforestation coupled with the destructive policies of Brazil’s far-right president, Jair Bolsonaro, could push the Amazon rainforest dangerously to an irreversible “tipping point” ... After this point the rainforest would stop producing enough rain to sustain itself and start slowly degrading into a drier savannah, releasing billions of tonnes of carbon into the atmosphere, which would exacerbate global heating and disrupt weather across South America.
(2023) https://www.nytimes.com/2023/01/04/magazine/amazon-tipping-p...
The consensus used to be that ecosystems are merely a product of prevailing weather patterns. But in the 1970s, the Brazilian researcher Eneas Salati proved that the Amazon, with its roughly 400 billion trees, also creates its own weather. On an average day, a single large tree releases more than 100 gallons of water as vapor. This not only lowers the air temperature through evaporative cooling; as Salati discovered by tracking oxygen isotopes in rainwater samples, it also gives rise to “flying rivers” — rain clouds that recycle the forest’s own moisture five or six times, ultimately generating as much as 45 percent of its total precipitation. By creating the conditions for a continental swath of evergreens, this process is crucial to the Amazon’s role as a global “sink” for carbon.
Many scientists now fear, however, that this virtuous cycle is breaking down.
While I certainly agree that chopping down the Amazon is terrible, I think you're vastly oversimplifying things with this theory. Some things just don't grow well in some places, and soil is important too. You can't just plant a bunch of trees in the desert: there's no soil there, just sand. Sure, you could start small at the coast and move inland as the ecosystem changes and soil quality is improved, but this is something that would probably take many centuries or longer.
Grasslands, savannas, etc. have been around for far, far longer than human civilization; they're not something we created with deforestation, and ruminants like cows(' ancestors) have been around far longer than us, grazing in these places. Chopping down forests to make more places for cows obviously is a bad idea, but I'm not convinced that it's feasible to take places that have been grazed by animals for millennia and somehow turn them all into nut tree forests.
I'm aware. There are methods like enhancing the sand with soil sludge (nutrients & microbiome), for example.
> something that would probably take many centuries or longer.
Destruction is fast, regeneration slow. Those deserts might as well be a product of previous civilizations overgrazing.
Environmental Implications of Livestock: Goats
https://epar.evans.uw.edu/research/environmental-implication...
Blame it on the goats? Desertification in the Near East during the Holocene
https://journals.sagepub.com/doi/full/10.1177/09596836166704...
> Grasslands, savannas ... they're not something we created with deforestation
Mongolia for example was much more forested in the past. Apx. 50% of current age grasslands and savannas were previously forests. Also, natural grazers prefer different plants than cows, so the compositions and storage capacity of pastures and grasslands differ extremely.
> I'm not convinced that it's feasible to take places that have been grazed by animals for millennia and somehow turn them all into nut tree forests
We don't have to. Just afforest those pastures and rewild the rest. It would protect the biodiversity for future generations.