When do more trees mean more water? A soils perspective

[Sheil, Douglas]

I hope this is of value to some of you and you may like to share more widely.

 

Our new publication led by @Sampurno Bruijnzeel challenges a harmful yet persistent myth--that is 'that more trees means less water'.

 

See the full paper available open access here (updated link to corrected version): https://www.sciencedirect.com/science/article/pii/S2197562025000855?via%3Dihub

Summary argument (from my LinkedIn post)--Reality is nuanced: Various studies of extensive monoculture plantations in dryland settings have indeed shown negative impacts on local moisture availability. But in many other contexts, forests improve soil infiltration and water retention, which supports groundwater recharge and dry-season flows. In various coastal/mountain areas, forests capture substantial moisture from fog and clouds too.

Our analysis--considering soil but ignoring atmospheric relationships--shows that forest restoration will likely improve dry-season water flows in 10-20% of areas currently available for reforestation—typically those with deep soils and seasonal rainfall.

Of course, extensive forest recovery (especially natural forests) would likely bring much greater benefits through enhanced rainfall recycling and other effects—but aspects of these relationships remain more controversial and challenging to predict and wasn't our focus here (I've written extensively on that in other posts, for example). There can also be substantial benefits from scattered tree cover (example).

The impact of forest and forest restoration on water depends on climate, soil conditions, degradation levels, and restoration approaches. In many cases, especially in degraded seasonal landscapes, restoration can be a win-win for both ecosystems and water security.

The science is clear: context matters.

Please share widely to those who can benefit.

 

Thanks

Douglas