cooler, moister, greener – Watts Up With That?

From Climate Etc.

by Douglas Sheil

Last week an article in Science, by Seo and colleagues, provided compelling evidence that the world’s land surface is getting drier. This global drying averaged a loss across all land surfaces of over two centimeters of water in two decades.

The trends suggest these losses continue. The authors highlighted the role of climate warming in this desiccation and claimed the changes are “permanent”. https://lnkd.in/eUV82jjV
This claim of permanence was repeated uncritically in a shorter commentary piece in the same issue of the journal. https://lnkd.in/e5r2_4mp

Pierre L. Ibisch and I see these trends differently. The changes may indeed be permanent but they needn’t be. It’s up to us. The role of land cover has been overlooked and is key. It wont be easy but with sufficient effort we should be able to fix this.

We submitted our comments to Science and the text is now appended below the online version of the original article (an “eLetter”). It is open access if you click through here: https://lnkd.in/eUV82jjV

The Earth is drying. Seo et al. (1) highlight an alarming shift: while for most of the planet’s history, a warming climate brought a wetter, greener world (2, 3), it now brings desiccation (1, 4). Our biosphere’s water-regulating functions are broken.

“While climate science and policy focus on greenhouse gases, they often neglect vegetation’s role in keeping the planet cool and hydrated. Forests, wetlands, and other ecosystems regulate temperatures and drive the water cycle (5) — but degradation has impaired these services. Feedbacks from droughts, heatwaves, and declining vegetation now amplify local and regional warming (6, 7). Nonlinear responses risk abrupt shifts and catastrophic tipping points (8, 9).

Solutions become clear when we recognise water and vegetation as partners in climate regulation. Protecting and restoring forests and wetlands does more than sequester carbon — it rebuilds the processes that keep landscapes cool, moist, and productive. Managing land to increase infiltration, reduce runoff, and restore soil water storage helps sustain transpiration and cool the land (5, 9-11). We need to revive a “sponge planet” (12) and support place-based innovations like “sponge cities” that enhance water retention where it’s most needed (13).

Policymakers must act boldly to safeguard “green water” (5, 14). Land-use decisions must prioritise ecosystems that regulate moisture and climate. Strong incentives are essential: those who degrade should pay; those who protect and restore must be rewarded. The message is simple and urgent: a cool, moist, green planet is our best defence against a drier, warmer world. It remains possible. The time to act is now.

References

1. K.-W. Seo et al., Science 387, 1408-1413 (2025).
2. U. Salzmann et al., Palaeogeography, Palaeoclimatology, Palaeoecology 309, 1-8 (2011).
3. M. T. Clementz, J. O. Sewall, Science 332, 455-458 (2011).
4. P. De Luca, M. G. Donat, Geophysical Research Letters 50, e2022GL102493 (2023).
5. D. Ellison et al., Global Environmental Change 43, 51-61 (2017).
6. C. Smith, J. C. A. Baker, D. V. Spracklen, Nature,  (2023).
7. D. L. Schumacher, J. Keune, P. Dirmeyer, D. G. Miralles, Nature Geoscience 15, 262-268 (2022).
8. T. M. Lenton et al., Proceedings of the national Academy of Sciences 105, 1786-1793 (2008).
9. A. M. Makarieva et al., Global Change Biology 29, 2536–2556 (2023).
10. D. Ellison, J. Pokorný, M. Wild, Global Change Biology 30, e17195 (2024).
11. D. Sheil, Forest Ecosystems 5, 1-22 (2018).
12. K. Yu, E. Gies, W. W. Wood, Nature Water, 1-3 (2025).
13. Z. Zheng, X. Zhang, W. Qiao, R. Zhao, Water Resources Management, 1-15 (2025).
14. L. Wang-Erlandsson et al., Nature Reviews Earth & Environment 3, 380-392 (2022).