Wednesday, April 1, 2020

April 2020 Science Journal Article Summary

Cherry tree in bloom

I'm guessing that most of you are reading more science while stuck at home, but that you're focusing on science related to the pandemic. I certainly am.

But for now, I figured I'd send the usual kind of summary (focused on protected areas this month), since this is where my expertise lies. I thought of reviewing some articles on how conservation can both help and hurt infectious disease transmission (depending on context), but that felt crass.

If you have thoughts on these summaries (if they should pause, change, etc. during the pandemic) please let me know. If you know someone who wants to sign up to receive these summaries, they can do so at

Hannah et al. 2020 estimates that effectively conserving 30% of tropical land could cut predicted species extinction by ~1/2-2/3 (if the conserved areas are both cited ideally and managed well: this is not about legal protection alone). Conserving 50% could reduce extinction by more like 2/3-80% (see Table 1 for details including how this varies by region). This is useful to understand how effective conservation can be at different scales. But it's important to note that citing PAs in ideal locations continues to be elusive, this model relies on fairly simple assumptions using species-area curves, and the fact that the results didn't vary much with climate change (RCP2.6 vs RCP 8.5) is concerning. Nonetheless, this could be motivating to highlight the importance of protecting and managing enough of the right places on earth to slow species extinction.

How well does the current network of protected areas represent both biodiversity and the provision of ecosystem services in the tropics? Neugarten et al. 2020 has answers for five countries (Cambodia, Guyana, Liberia, Madagascar, and Suriname). They found that PAs are doing pretty well on biodiversity, forest protection, and forest carbon stocks, although with lots of room for improvement (Table 3). But PAs are not doing well on protecting non-timber forest products (like food and medicine) nor freshwater ecosystem services, both of which are mostly protected at about the same rate as land overall in each country (except Cambodia which did somewhat better on freshwater ecosystem services). Identifying opportunities to improve like this is critical to inform where to cite future PAs. They are up front about a few caveats: they looked only at designation of formal protected areas (rather than effective management on the ground), this may not be reflective of PAs across the tropics more broadly, and they had to rely on some squishy data (e.g. a mix of data sources and expert input to identify biodiversity priority areas). But it's still a good step to inform citing the next wave of PAs as interest in doing so ramps up across the globe. The authors have shared their data here: and are happy to help others to access and use it.

Wilhere 2008 makes an important point about analyses of how much conservation "is enough." He argues there's no single answer, since it depends on society's values for things like what risk of extinction is acceptable. Another key point is that the inputs into these models (which spp. or habitats to model and prioritize) are inherently value-driven as well. He recommends that these kinds of analyses: are transparent about the role of ethics / values (outside of science) in choosing conservation targets, recognize that any modeled policy options are only one of many possible choices, consider alternative targets to prioritize, and work with economists to produce cost estimates of any recommendations.

Wilhere et al. 2012 is a critique of one of the many 'half earth' papers arguing we need to effectively conserve at least half of the earth to avoid unacceptable biodiversity loss (Noss et al. 2012). The critique is similar to the Wilhere 2008 paper: the half earth target is presented as a "strict scientific point of view" without recognizing the value judgments that inform the results. They call for papers like Noss' to clearly articular the values of the author, and evaluate multiple policy options reflecting different values.

Finally, Armsworth et al. 2020 looks at  the best "bargains" exist for conservation: where the most species can be protected (from projected land conversion) for the lowest cost of land acquisition. In other words, how can we prevent the most species loss with a fixed budget for protection?
The new spatial prioritization model this is based on goes beyond binary models (which recommend protection or not), and instead allocates funding as a continuous variable. It also considers complementarity to avoid concentrating funding in areas rich with the same species. When they run the model for the coterminous U.S., attempting to conserve all species equally leads to the Southwest being a priority (since there's lots of cheap, intact habitat). But focusing on vertebrates vulnerable to extinction, priorities pop out in Texas (due to cave ecosystems with many unique & threatened species in small places) and the Southern Appalachians. There's a great discussion of how different assumptions and data inputs impact the results. There's a blog about this article here:

Richter et al. 2020 has two key points about water scarcity (and the resulting impact on freshwater ecosystems) in the Western United States. First, cattle feed is the biggest driver - 1/3 of water consumed in 17 Western states is for cattle feed, and in the Colorado River basin it's 55% (Table 1). But in good news, there is a proven affordable solution - paying farmers to temporarily fallow (stop growing crops) some or all of their land used for cattle feed. We also would need to reduce some of the water transferred between basins to fully address the over-allocation of water. The paper also has good data on which cities are driving the most scarcity via demand for beef, impact of water scarcity on fish (including extinction risk), and the cost of payments to farmers for fallowing ($82-241 million / year). Finally, one of the authors (Arjen Hoekstra) passed away last year, and I wanted to express how much I appreciate his pioneering work on water footprinting, and how much influence he had on me as a scientist. He will be sorely missed.

Hammerschlag et al. 2019 is a great overview of the many ecological functions and ecosystem services provided by aquatic predators (both marine and freshwater). It's well written enough to serve as a good introduction to the topic even for people like me with very little marine ecology background. Most of the benefits are fairly obvious, but benefits to climate mitigation (by reducing herbivores that can reduce carbon sequestration and storage) and inspiring products like boat coatings to reduce drag were especially interesting.

Armsworth, P. R., Benefield, A. E., Dilkina, B., Fovargue, R., Jackson, H. B., Le Bouille, D., & Nolte, C. (2020). Allocating resources for land protection using continuous optimization: biodiversity conservation in the United States. Ecological Applications, eap.2118.

Hammerschlag, N., Schmitz, O. J., Flecker, A. S., Lafferty, K. D., Sih, A., Atwood, T. B., … Cooke, S. J. (2019). Ecosystem Function and Services of Aquatic Predators in the Anthropocene. Trends in Ecology & Evolution, 34(4), 369–383.

Hannah, L., Roehrdanz, P. R., Marquet, P. A., Enquist, B. J., Midgley, G., Foden, W., … Svenning, J. (2020). 30% Land Conservation and Climate Action Reduces Tropical Extinction Risk By More Than 50%. Ecography, 1–11.

Neugarten, R. A., Moull, K., Martinez, N. A., Andriamaro, L., Bernard, C., Bonham, C., … Turner, W. (2020). Trends in protected area representation of biodiversity and ecosystem services in five tropical countries. Ecosystem Services, 42(January), 101078.

Richter, B. D., Bartak, D., Caldwell, P., Davis, K. F., Debaere, P., Hoekstra, A. Y., … Troy, T. J. (2020). Water scarcity and fish imperilment driven by beef production. Nature Sustainability.

Wilhere, G. F. (2008). The how-much-is-enough myth. Conservation Biology, 22(3), 514–517.

Wilhere, G. F., Maguire, L. A., Scott, J. M., Rachlow, J. L., Goble, D. D., & Svancara, L. K. (2012). Conflation of Values and Science: Response to Noss et al. Conservation Biology, 26(5), 943–944.

Stay safe, vigilant, and healthy,


p.s. If you'd like to keep track of what I write as well as what I read, I always link to both my informal blog posts and my formal publications (plus these summaries) at