Monday, October 3, 2022

October 2022 science summary

Calli & Jon on porch


This month I am summarizing two science articles on climate change and one on conservation prioritization

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Belote et al. 2021 is a great analysis comparing how different ways of identifying spatial conservation priorities overlap and conflict in the lower 48 states of the US. They focus on 4 groups of vertebrates (mammals, birds, amphibians, and reptiles), and 4 methods of prioritizing: species richness, rarity-weighted richness, and two Zonation approaches that favor complementarity / representation (ABF favors species richness, CAZ favors rarity). Fig 1 has the most interesting maps if you want to compare the approaches, and Fig 3 highlights the places with the most agreement across models that they are in the top 30% of options. It's a great way to see how your values and methods can affect your results (but also that some places are pretty agreed on priorities). Two things to contrast with the NatureServe "map of biodiversity importacet" - that analysis includes plants and some invertebrates (this does not), and NatureServe focuses on imperiled species while this is threat-blind. One last note on the zonation approaches - these work best as a complete set; if you pick and choose among them they don't perform nearly as well, and it's rare that science recommendations are ever taken up entirely. But conversely a focus solely on richness or rarity misses lower diversity ecosystems and wide-ranging species.

Temmink et al. 2022 is an overview of carbon storage and cycling in wetlands. They note peatlands and coastal wetlands have much higher carbon stock density than forests or oceans, and also sequester more carbon each year (see the figure in the Review Summary for a nice overview, or Fig 1 for more detail). They also focus on how healthy wetlands have feedbacks that support high productivity and/or low decomposition (see Fig 2), but that people are disrupting those feedbacks. They show how much of these ecosystems have been lost already, and how fast they are disappearing (Table 1) and estimate this amoutns to 500 million metric tons of C lost each year. They closeby arguing that keeping wetlands intact is key for climate mitigation. One caution though - they focus only on carbon, and some wetlands emit quite a lot of methane and nitrous oxide. Those are much stronger GHGs than CO2, so the net climate benefit of wetlands is smaller than you'd think from looking at carbon alone.

Law et al. 2018 is an analysis of how more trees in Oregon (planting, cutting less often, and halting cutting) can lead to more climate mitigation benefits and cobenefits of water availability (maybe, stay tuned on that). From 2011-2015, OR forests already on net sequestered the equivalent of 72% of OR's total GHGs (Fig 2), and they think that could be boosted by 56% with a series of programs. See Figure 3 for this potential, but note the bars each represent a single decade (and the lower figure is annual change within that decade), with cumulative results from 2015-2100 showing up as numbers in italics OVER the bars. This confused me pretty thoroughly, and it looks to me from the Figure like annual "net ecosystem carbon balance" (~=net carbon sequestered) by 2100 would increase by ~1.2 Tg C / yr, not the 2-3 they say in the text. They also find that using harvest residues for bioenergy would lead to a net increase in emissions (even assuming 1/2 of residues replace coal or natural gas). One thing that struck me as very odd: they propose afforesting grass crops which are irrigated but not used for food or forage, and claiming water will be freed up by doing so. But I can't figure why someone would irrigate grass if it wasn't used for food (or things like lawns or golf courses which forests wouldn't be compatible with)- maybe it's literally fields to produce grass seed sold for lawns?
Peter Ellis from TNC had this take which I found helpful (that this shouldn't be taken as having national implications): "The study is constrained to the Pacific Northwest (PNW). If you care about carbon, you can never really beat leaving a PNW forest alone. No attempts to sell the idea of mitigation through bioenergy or wood product storage are going to beat carbon storage in forests in a region where: 
•    Trees are largest in the world
•    They take forever to decompose, so coarse woody debris storage is really important.
Their proposal for Oregon’s forest actually makes a lot of sense to me: 'reforestation, afforestation, lengthened harvest cycles on private lands, and restricting harvest on public lands increased net ecosystem carbon balance by 56% by 2100'"


Belote, R. T., Barnett, K., Dietz, M. S., Burkle, L., Jenkins, C. N., Dreiss, L., Aycrigg, J. L., & Aplet, G. H. (2021). Options for prioritizing sites for biodiversity conservation with implications for “30 by 30.” Biological Conservation, 264, 109378.

Law, B. E., Hudiburg, T. W., Berner, L. T., Kent, J. J., Buotte, P. C., & Harmon, M. E. (2018). Land use strategies to mitigate climate change in carbon dense temperate forests. Proceedings of the National Academy of Sciences, 115(14), 3663–3668.

Temmink, R. J. M., Lamers, L. P. M., Angelini, C., Bouma, T. J., Fritz, C., van de Koppel, J., Lexmond, R., Rietkerk, M., Silliman, B. R., Joosten, H., & van der Heide, T. (2022). Recovering wetland biogeomorphic feedbacks to restore the world’s biotic carbon hotspots. Science, 376(6593).

p.s. This is a recent picture of me and my neighbor's adorable snaggletoothed dog Calli on our porch (we were dogsitting).