Monday, January 1, 2018

January 2018 science journal article summary

Happy new year! Here are a handful of articles focused on global agriculture analyses, plus one with bad news on climate change, and a 2018 #MyScienceResolution. 

Cauliflower, romesco, and broccoli at the farmer's market

 I also want to pass on a cool resource Eddie Game alerted me know. It's a tool to help you figure out which journal to submit a paper to:  You enter the title and abstract of your paper and it gives you a list of appropriate journals. You may also want these tips on how to write an abstract to get found easily in Google and Google Scholar:

On to the articles!

Somehow I'd missed West et al 2014, which is a great (and very short) summary of opportunities to improve agriculture around the world. Just looking at the two figures is highly educational: Fig 1 shows the potential to increase yields on poorly performing croplands to even 50% of their potential yields (which would provide enough food for 850 million more people, while still leaving plenty of room to improve), and Fig 2 shows how much we can reduce environmental impacts of ag in key regions without reducing yields. The spatial patterns aren't surprising, but the specific numbers are highly motivating. For example, China alone produces 28% of global N2O emissions (a potent greenhouse gas). Reducing excessive nutrients and improving water efficiency of crops around the world would have a big impact, as would reducing the amount of animal products we eat and the amount of food that is wasted. Be sure to check out the supplement for more great maps.

Phalan et al 2016 tackles a tricky problem at the heart of TNC's work with ag: how can we ensure that intensification reduces conversion rather than incentivizing it through higher profits? It's under two pages, so I'd recommend just reading it. But the mechanisms they propose to boost yield and promote nature are: 1) land use zoning (specify land for ag and land for conservation, as Costa Rica did), 2) use payments, subsidies, or land taxes (e.g. a program in India where herders set aside habitat in exchange for insurance and technical assistance), 3) "spatially strategic" deployment of tech / infrastructure / ag knowledge (e.g. focusing on staple crops which have more stable demand), and 4) standards (including voluntary ones) and certification. I found this to be good food for thought about how TNC could tighten our theory of change.

Hanspach et al 2017 looks at trade-offs between food security and biodiversity for ag in the "global south" (developing countries). They surveyed 110 self-reported experts and looked for patterns. Surprisingly, while in many landscapes there were clear trade-offs between food security and biodiversity, several respondents reported other cases where the two goals were linked (either in "win-win" or "lose-lose" cases). Figure 2a shows where each landscape fell. Infrastructure, market access, and financial resources were all associated with poor biodiversity but good food security, meaning investment in intensification on its own will likely not lead to conservation outcomes. Social equity and land access were found to be necessary but not sufficient for both food and biodiversity goals. Relying on expert assessments isn't a replacement for good empirical data, but this still has useful elements for TNC to incorporate in our ag work.

Gerber et al 2016 is a global analysis of N2O emissions from croplands. The key point is that areas with very low N use and production can use much more fertilizer with relatively small increases in N2O emissions, while areas with high N excess can use a little less to get big reductions in N2O. For example, cutting N application by 5% in Shandong province (China) would reduce N2O by 9%. Be sure to check out Table 2 (N application totals and rates by country) and Fig 3 (N2O emissions per unit of N applied at a sub-national level), and fig 4 if you're interested in specific crops. Note that they used a new approach which in general predicts significantly lower emissions than other models (they go over several caveats in detail).

Zomer et al 2017 estimates that globally cropland soils could sequester 0.90-1.85 Pg C / yr (1 Pg = 1 billion metric tons) for at least 20 years. This estimate derives from how much soil C has been lost relative to historic levels, along with estimates from an earlier paper of how much sequestration can be achieved through a range of conservation practices (e.g. cover cropping, conservation tillage, rotational grazing, etc.). Table 2 and Figure 2 show where the authors see the most room for improvement (the Midwest US, India, and Europe in particular). TNC's Deborah Bossio is second author so she should be able to answer any questions you may have.

A new paper from NatureNet fellow Kyle Davis (2017) investigates the impact of changing and moving crops on existing croplands around the world to improve yield and reduce water consumption. The hypothetical optimal crop patterns consumed 14% less rainwater and 12% less "blue" water (irrigation from surface and ground), while also producing 10% more calories, 19% more protein, and other benefits. A big caveat is that this involves not only shifting what is grown where (already a big task) but also shifting how much we produce of each crop. For example, they cut production of wheat, rice, corn, and sugar in favor of more soy and tubers (like potato and sweet potato). The interesting part to me is thinking about how this approach could be used in a national land use planning exercise with more realistic constraints.

Brown & Caldeira 2017 has some bad news about climate change. They looked at several climate models and scenarios and evaluated how well they predicted the recent past (looking at 9 variables, not just temperature). They predict warming ~15% higher than currently predicted and have a narrower confident interval for predictions. For climate wonks, they note that emissions in line with the RCP 4.5 scenario are likely to produce warming previously associated with RCP 6.0. There are several important caveats in the discussion, but this nonetheless raises the urgency to take aggressive action on climate to minimize the projected impacts. Take a look at Figuyre 2 which shows the new narrower predictions in red for different emissions scenarios. You can read an overview of the paper here or a longer blog from the authors here:


I haven’t read the Pelger 2017 study it’s based on, but this blog post gave me an idea for a 2018 science resolution! Essentially students writing for a non-scientific audience found that it helped their science writing as well. So if you work as a scientist, commit to writing a blog, or talking to your friends and family about your work without making their eyes glaze over! I'm going to shoot for my next peer-reviewed article to be readable by an ordinary human being. If you need more motivation, check out this inspirational talk by Dan Rather with a vision for a revolution in science communications as a foundation for changing how we think about truth and “fake news” in society: (thanks to Laurel Saito for the link).

Brown, P. T., & Caldeira, K. (2017). Greater future global warming inferred from Earth’s recent energy budget. Nature, 552(7683), 45–50.

Davis, K. F., Rulli, M. C., Seveso, A., & D’Odorico, P. (2017). Increased food production and reduced water use through optimized crop distribution. Nature Geoscience, 10(12), 919–924.

Gerber, J. S., Carlson, K. M., Makowski, D., Mueller, N. D., Garcia de Cortazar-Atauri, I., HavlĂ­k, P., … West, P. C. (2016). Spatially explicit estimates of N2O emissions from croplands suggest climate mitigation opportunities from improved fertilizer management. Global Change Biology, 22(10), 3383–3394.

Hanspach, J., Abson, D. J., French Collier, N., Dorresteijn, I., Schultner, J., & Fischer, J. (2017). From trade-offs to synergies in food security and biodiversity conservation. Frontiers in Ecology and the Environment, 15(9), 489–494.

Phalan, B., Green, R. E., Dicks, L. V., Dotta, G., Feniuk, C., Lamb, A., … Balmford, A. (2016). How can higher-yield farming help to spare nature? Science, 351(6272), 450–451.

West, P. C., Gerber, J. S., Engstrom, P. M., Mueller, N. D., Brauman, K. A., Carlson, K. M., … Siebert, S. (2014). Leverage points for improving global food security and the environment. Science, 345(6194), 325–328.

Zomer, R. J., Bossio, D. A., Sommer, R., & Verchot, L. V. (2017). Global Sequestration Potential of Increased Organic Carbon in Cropland Soils. Scientific Reports, 7(1), 15554.

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