September 2025 science summary

Hi there,

This month I've got three articles on water scarcity, and two on fire and human health in South America. But before I get to the science, here are a couple of very old blog posts and more pictures...

In case you want more pics like the one above, here's an album full of similar pics of snowy mountains and clouds I took on the flight from Punta Arenas (Chile) to Santiago. This was the most beautiful plane flight I've ever taken.

Also, way back in 2013 I wrote an article about how I came to appreciate house centipedes (along w/ nematodes) for their ecological role in pest control, and recently was tickled to see people are still reading and commenting on it 12 years later! Here it is if anyone is curious: https://blog.nature.org/2013/02/08/everyday-nature-how-i-came-to-love-house-centipedes

Finally, the Washington Post and New York Times recently did their own taste tests about real sugar / high fructose corn syrup (including Mexican vs. American Coke) BUT neither was double-blind and neither involved multiple samples of each to improve statistical confidence in the results. Here's one way to do a more rigorous test if you're interested: https://sciencejon.blogspot.com/2012/10/does-real-sugar-make-mexican-coke-taste.html

If you know someone who wants to sign up to receive these summaries, they can do so at http://subscribe.sciencejon.com (no need to email me). OK, with that, here are the science summaries (finally):

FIRE AND HUMAN HEALTH:
dos Santos et al. 2025 found that the smoke plumes from the 2020 Pantanal fire combined with heatwaves, lack of rain to wash smoke particles from the air, and COVID to drive an increase of 21% in premature non-COVID deaths in São Paulo state (see Fig 5) – not counting nonlethal hospitalizations. In other words, improved fire management in the Pantanal could benefit even city dwellers far away. Fig 2 shows the smoke plume trajectories, Fig 3 shows the resulting PM2.5 (small particulate matter air pollution) levels, and Fig 7 is a nice schematic of how the different hazards combine to drive excess mortality. The authors call for more widespread integrated fire management, and continued reductions in sugarcane burning.

Palmeiro-Silva et al. 2025 is an opinion piece arguing that with wildfires increasing across South America, we need to do more to consider human health impacts of fire prevention and management. Using the 2024 wildfires in the Pantanal and the Amazon as a case study, they note that in addition to impacts on the environment and obvious human health impacts like death and air pollution, economic and mental health impacts are also important. They call for better and faster communication to affected communities, co-development of fire plans with local residents, and coordination across multiple sectors to address wildfires via a comprehensive fire risk reduction strategy.


WATER SCARCITY:
Womble et al. 2025 covers several potential ways to address water scarcity (via mandatory cutbacks, several types of water markets focused just on water consumption, and strategically considering impact on fish habitat when selecting places to buy water from). Fig 3 shows the room for improvement from the perspective of fish, often with relatively little extra cost. But an interesting twist is that depending on how the market is structured, the cost and incentives to consider fish habitat varies a lot. The default least cost "authorized market" authorized by the 2019 legislation is not great for fish (the "strategic portfolio" would cost 55% more) but for other markets the extra cost is from <1% to 8% higher to improve fish habitat. Specifically: "strategically investing <1% more funding than a least-cost plan nearly doubles fish habitat improved to intermediate status in an authorized water market with aggressive water-use reductions" and "investing 8% more than a least-cost plan ... nearly triples restored intermediate habitat in an expanded water market with aggressive water-use reductions, more water-user participation and more protections for restored flows". Finally - just 10 transactions yield 1/4 of that potential tripled habitat benefit at 1% of the cost. My overall take-aways are that there could be a lot of secondary effects of market structure, and that a little bit of focused spending to improve fish habitat can have a huge impact!

Given the outsize impact of alfalfa in the SW states, Waring et al. 2025 has some potentially useful ideas about how IF you had a well-designed water market, alfalfa irrigation could be reduced to save water (compensating farmers for reduced yield). Essentially they would cut and sell alfalfa fewer times each year b/c it goes dormant under low water, which they estimate could reduce 16-50% of alfalfa’s water use. See Table 3 for why that’s a big range – it depends on how many fields participate, how many cuttings participating fields have under BAU, and assumptions of irrigation efficiency. Almost half the fields have a short season (3-4 cuttings), which is why in Table 3 you see that scenarios like 3 and 5 that reduce participation by short-season fields result in a lot of missed opportunity. Fig 2d shows the % of total water consumption in each state due to alfalfa from Jul-Oct (note consumption is the amount of water evaporated and transpired from both rain and irrigation, unlike withdrawal which is the volume of irrigation water applied). 

Coelho et al. 2025 shows the trend for overall streamflow and flooding in the Pantanal, and also shows how three upland basins (Jauru, Taquari, and Miranda) connect to their floodplains and the Upper Paraguay (UP) River. I find Fig 11 to be pretty compelling in showing the drying trend for the Pantanal, and Fig 3 shows how the three upland basins flow into their respective floodplains and then to the UP river channel.


REFERENCES:
Coelho, M. E. M. S., Chaves, H. M. L., & Fonseca, M. R. (2025). Trends, Patterns, and Persistence of Rainfall, Streamflow, and Flooded Area in the Upper Paraguay Basin (Brazil). Water, 17(10), 1549. https://doi.org/10.3390/w17101549

dos Santos, D. M., de Oliveira, A. M., Duarte, E. S. F., Rodrigues, J. A., Menezes, L. S., Albuquerque, R., Roque, F. de O., Peres, L. F., Hoelzemann, J. J., & Libonati, R. (2024). Compound dry-hot-fire events connecting Central and Southeastern South America: an unapparent and deadly ripple effect. Npj Natural Hazards, 1(1), 32. https://doi.org/10.1038/s44304-024-00031-w

Palmeiro-Silva, Y., Llerena-Cayo, C., Blanco-Villafuerte, L., Rojas-Rueda, D., Borchers Arriagada, N., Vela-Clavo, Z., de Camargo, T., Rusticucci, M., Valdes-Velasquez, A., & Hartinger, S. M. (2025). The 2024 South America ablaze: health impacts and policy imperatives for protecting population health in an era of wildfires. The Lancet Regional Health - Americas, 48, 101160. https://doi.org/10.1016/j.lana.2025.101160

Waring, E., Dahlke, H. E., Abatzoglou, J. T., Medellín-Azuara, J., Yost, M. A., Bali, K. M., Naughton, C. C., Putnam, D. H., Sabie, R., Kishore, S., Santos, N. R., & Viers, J. H. (2025). Reimagining alfalfa as a flexible crop for water security in the Southwestern USA. Science of The Total Environment, 990(June), 179851. https://doi.org/10.1016/j.scitotenv.2025.179851

Womble, P., Gorelick, S. M., Thompson, B. H., & Hernandez-Suarez, J. S. (2025). A strategic environmental water rights market for Colorado River reallocation. Nature Sustainability. https://doi.org/10.1038/s41893-025-01585-x


Sincerely,
 
Jon
 
p.s. The pic above is one of the many beautiful snow covered mountains I saw in Chile between Punta Arenas and Santiago (in June so during winter). More pics are here: https://www.flickr.com/photos/jaundicedferret/albums/72177720327724315/with/54674270850