Monday, April 1, 2024

April 2024 Science Summary

Art at the Kennedy center


Just three articles this month: how wetland restoration affects climate mitigation, how climate change is affecting seasonality of river flow, and a summary of how people use plants around the world.

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Schuster et al. 2024 reviews the net climate impact of wetland restoration, considering carbon, methane, and nitrous oxide. Their headline is that it takes 525 years for restoring peat to result in net climate cooling (b/c short-term methane increases offset the carbon gains), and 141 years for non-peat wetlands (marshes, riparian wetlands, and swamps). They argue other more positive estimates have left out nitrous oxide. BUT they are looking just at the restoration over time NOT comparing restored wetlands to the baseline of degraded wetlands (since drained peat also emits methane and lots of CO2, the time would be a lot shorter to be net climate cooling. Some other papers I've read (e.g., Richardson et. al 2022 on pocosin) found minimal methane emissions making restoration a clear winner even in the short term. I asked a couple experts about this paper and they also flagged that while in the short term we should be worried about methane, it's also true that: the alkalinity export from peat could make them MORE cooling than we think, and that there are other ecosystem services to consider.

Wang et al. 2024 looks at how climate change has changed the seasonality of river flow (how much it varies month to month, including frequency of droughts and floods). They found that ~14% of long-term river gauges show changes in seasonality over the last 50 years that isn't driven by changing annual precipitation. The surprise is that seasonality is mostly DECREASING counter to the narrative of more floods and droughts (see Fig 1 for a map of results, and Fig 2 which adds detail). In their figures brown means less seasonality (more even flow): "L+" means low flows become higher flows (NOT higher frequency of drought) while "H-" means floods see lower flood volume (again NOT lower frequency of flood events). You'll see most of North America, most of Europe, and some of Russia have seen reduced seasonality in recent decades. Blue means MORE seasonality, focused in: SE Brazil, some European countries, and in the US the SE and some of the Rocky Mountains. The explanation is worth reading in full, but in brief: 1) snow melting earlier means less runoff from snow at the same time as spring rains, 2) early spring greening means more water gets transpired, 3) it's more complicated in places not dominated by snowmelt.

Pironon et al. 2024 is a global analyis of plants used by humans (directly or indirectly - medicinal uses dominate but they look at nine other types of use, see Fig 2). See Fig 1a for a map of how many plant species are used around the world. They find 1) people use more plant species in places where most plant species exist, 2) Indigenous lands use slightly fewer species than neighboring non-Indigenous regions, and 3) protected lands use slightly fewer species than non-protected lands. These are correlations - they don't control for income or many other covariates. And from a conservation perspective we may not want all species to be used, especially rare ones!Note there are some problems with the data, e.g., Figure S1 shows how poor the sampling density is outside of the US, Central America, Europe, and Australia. Finally, they only found 971 species of plants that provide food to bugs we use (honeybees, silkworms, lac insects, and grubs) which seems really low. There's an article about this at:

Pironon, S., Ondo, I., Diazgranados, M., Allkin, R., Baquero, A. C., C├ímara-Leret, R., Canteiro, C., Dennehy-Carr, Z., Govaerts, R., Hargreaves, S., Hudson, A. J., Lemmens, R., Milliken, W., Nesbitt, M., Patmore, K., Schmelzer, G., Turner, R. M., van Andel, T. R., Ulian, T., … Willis, K. J. (2024). The global distribution of plants used by humans. Science, 383(6680), 293–297.

Schuster, L., Taillardat, P., Macreadie, P. I., & Malerba, M. E. (2024). Freshwater wetland restoration and conservation are long-term natural climate solutions. Science of The Total Environment, 922(August 2023), 171218.

Wang, H., Liu, J., Klaar, M., Chen, A., Gudmundsson, L., & Holden, J. (2024). Anthropogenic climate change has influenced global river flow seasonality. Science, 383(6686), 1009–1014.

p.s. This photo is of a sculpture at the Kennedy Center by ByeongDoo Moon called "I have been dreaming to be a tree"