Monday, February 1, 2021

February 2021 science summary

Broken apple slicer


I couldn't resist sharing the image above. When my apple slicer broke, the result seemed very nightmarishly 2020 (a piece of fruit full of sharp metal)!

I've got 5 articles on freshwater this month, plus one on conservation planning across land and sea. Also, if you missed the panel discussion I hosted about how scientists can improve their impact (with Lynn Scarlett, Yoshi Ota, Christian Pohl, and Mark Reed), I learned a lot so recommend it! The recording is available here: and their combined high-level advice is here:

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The findings of Leal et al. 2020 may seem obvious, but they're important to highlight: conservation planning focused on terrestrial species only does a poor job at protecting freshwater biodiversity. They did some modeling in Brazil to look at trade-offs between freshwater and terrestrial species, and how to improve planning. Their low-bar recommendation is that even without data on freshwater biodiversity, just considering aquatic connectivity in additional to terrestrial species roughly doubles the benefit to freshwater species with almost no decrease in terrestrial benefits (Fig 3e & 3f, purple lines). If planning considers both terrestrial and freshwater biodiversity data, about a 5% decrease in terrestrial benefits leads to a ~400% increase in freshwater benefits (Fig 3e & 3f, aqua lines). This represents a strong case against assuming terrestrial work will do a good job at protecting freshwater ecosystems, and the idea of just including aquatic connectivity is an appealing entry point in places where better freshwater data are unavailable.

Improving water quality in agricultural landscapes (and downstream water bodies like the Gulf of Mexico) can be accomplished via changing inputs (e.g., using less fertilizer, or applying more stable forms at the right times), soil management to keep soil and nutrients in the field, edge-of-field practices like riparian buffers that intercept runoff, and through in-stream wetlands. Cheng et al. 2020 modeled how much nitrogen (N) wetlands remove from streams in the US (860,000 metric tons / year, and found that 10% more wetlands (+5 million hectares) could double N removal if they were in the right places (See Figs 3 & 5, although there are no big surprises here). This builds on other work about the essential role of wetlands in removing water pollution in concert with work on farms (e.g. Tomer et al. 2015 in JEQ), but highlights the need for landscape-scale planning and optimization for restoration to be as effective as possible. But one reason there are fewer wetlands in watersheds losing lots of N is that farmland tends to be productive and expensive there, and their proposal to double N removal requires losing 2% of total US cropland area. The authors also don't account for the potential increase in nitrous oxide which is a potent greenhouse gas. If you don't have the appetite for the whole article, this 1-page summary (Finlay 2020) has more detail:

King et al. 2021 offer a model of the costs and benefits of removing river barriers (dams, culverts, canal locks, and even natural waterfalls) in southern England. They find the benefits of barrier removal exceed the costs, but note that benefits are only estimated via reported willingness to pay for improved species richness and abundance (which were lumped in with more publicly accessible river bank, which I think could skew the data). They estimated a cost of >53 million pounds to remove all 650 barriers on the river Wey. My real take away is that removing barriers is expensive, but if we trust reported WTP, there may be support for fees that go to barrier removal if it is likely to lead to better recreational opportunities.

Lin et al. 2020 is a overview of how historic canals impact aquatic ecosystems (both positively and negatively), and opportunities to improve their management for conservation. It's global but focused mostly in Europe and North America. Canals can harm biodiversity by providing entry to non-native species and pathogens, allowing interbreeding which reduces genetic diversity, and serve as 'ecological traps' by attracting species that will die or be heavily stressed during drought or other events. On the other hand, canals can help biodiversity by providing connectivity and migratory pathways when rivers are fragmented, as well as provide refuges from human disturbance and climate change in some cases. Regardless, thoughtful management (or intentional abandonment) can improve environmental outcomes if done well. See Fig. 3 for broad examples,  Table 1 for variables that can inform management, and Fig. 4 for which management options relate to different objectives. The authors note that canals can be challenging to balance the human needs that the canals were originally built for with conservation objectives.

Tulloch et al. 2021 used Marxan w/ Connectivity for a case study (in Papua New Guinea) that looks at connections across land and sea and highlights intersections (like how forests and inshore reefs are connected). The idea was to improve on planning focused on a single realm (marine or terrestrial or freshwater). Fig 1 is a flowchart of the process they used. While the title mentions freshwater, they had no freshwater goals, and instead only used rivers as a connection between ecosystems on land and sea.

Cheng, F. Y., Van Meter, K. J., Byrnes, D. K., & Basu, N. B. (2020). Maximizing US nitrate removal through wetland protection and restoration. Nature, 588(7839), 625–630.

Finlay, J. (2020). Making the most of wetland restorations. Nature, 588, 592–593.

King, S., O’Hanley, J. R., & Fraser, I. (2021). How to choose? A bioeconomic model for optimizing river barrier mitigation actions. Ecological Economics, 181(March), 106892.

Leal, C. G., Lennox, G. D., Ferraz, S. F. B., Ferreira, J., Gardner, T. A., Thomson, J. R., Berenguer, E., Lees, A. C., Hughes, R. M., Mac Nally, R., Aragão, L. E. O. C., de Brito, J. G., Castello, L., Garrett, R. D., Hamada, N., Juen, L., Leitão, R. P., Louzada, J., Morello, T. F., … Barlow, J. (2020). Integrated terrestrial-freshwater planning doubles conservation of tropical aquatic species. Science, 370(6512), 117–121.

Lin, H. Y., Cooke, S. J., Wolter, C., Young, N., & Bennett, J. R. (2020). On the conservation value of historic canals for aquatic ecosystems. Biological Conservation, 251(February), 108764.

Tulloch, V. J. D., Atkinson, S., Possingham, H. P., Peterson, N., Linke, S., Allan, J. R., Kaiye, A., Keako, M., Sabi, J., Suruman, B., & Adams, V. M. (2021). Minimizing cross-realm threats from land-use change: A national-scale conservation framework connecting land, freshwater and marine systems. Biological Conservation, 254(July 2020), 108954.


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