Monday, July 1, 2019

July 2019 science journal article summary

      Above: People floating down the river Rhine, see rivers articles below


Here is another grab bag of articles on landscape conservation, research impact, rivers, climate change, and coastal wetlands. If you know someone who wants to sign up to receive these summaries, they can do so at

Once again Steve Wood (from The Nature Conservancy) has kindly added a couple of his own guest reviews, which I've broken out below to avoid confusion. Thanks Steve!

Burivalova et al. 2019 is a literature review of how effective four strategies were in delivering environmental, social, and economic outcomes. They looked at creating protected areas (PAs), forest certification and reduced impact logging (RIL), payment for ecosystem services, and community forest management. The results are varied and complex but Figure 2 summarizes them very well - no strategies always succeed, but all sometimes succeed (and note the caveat that each square is not equivalent). PAs performed well environmentally (after certification & RIL), but very poorly socially and economically. The authors conclude that there are surprising gaps in the literature on monitoring the efficacy of conservation strategies, and that before implementation local evidence should be examined to minimize the chance of failure or even having a strategy backfire.

White et al. 2019 surveyed land managers from the U.S. Forest Service about how they received and used scientific information in decision making. One key finding is that they believe science is less useful in making decisions with high public consensus (although even then only 19% of managers thought public priorities should have more weight than science, with 36% wanting equal weight and the remainder giving more weight to science, see Figure 3a). This study also reports low engagement with scientists, but Figure 1 shows that they primarily measured managers actively seeking out scientists rather than the reverse (which could be more common).

Bogenschneider et al. 2019 interviewed legislators in WI and IN about how research contributes to policymaking. While research was only infrequently mentioned as changing or even informing their positions on issues, it was seen serving several purposes (see Table 1), including persuading others, designing good legislation, educating others, improving debate & dialogue, and building trust. However, several quotes imply that they tend to seek out research that backed up their beliefs rather than exploring with an open mind. At the same time, the results highlight the importance of clear scientific conclusions that allow legislators to evaluate the potential impacts of actions they're considering (as opposed to more circuitous findings sometimes favored by scientists).

Grill et al. 2019 estimates only about a third of the world's longest rivers (<1,000 km) are freely flowing (defined here with a new metric that means neither dammed, nor significantly impacted by water consumption or infrastructure in riparian areas and floodplains). Those long free rivers are mostly in remote parts of the Amazon, Arctic, and Congo. On the other hand, shorter river reaches are doing better: 56% of long rivers (500-1000km) are freely flowing, rising to 80% and 97% for medium (100-500km) and short (10-100km) rivers respectively. However, since they rely on global dam databases, they caution that they likely overestimate freely flowing rivers due to missing data on small dams. The figures (and table 1) have great details on how well connected each river reach is, what limits connectivity most (96% one of the impacts of dams: fragmentation, flow regulation, and sediment trapping), and connectivity broken down by river length.

Cui et al. 2016 estimates how sediment built up behind Matilija dam would be released after dam removal (or partial removal / breach). They conclude that upon removal the main sediment pulse is likely to only last a few hours, and almost certainly < 3 days (with a worst case scenario of 8 days). The authors then argue that halting water diversion (e.g. for agriculture) until the sediment stabilizes should have minimal impact given the short time for sediment to be flushed out.

Gonzalez 2018 is an unsurprising but interesting reframing of current and projected climate change impacts: national parks are harder hit than the rest of the US (getting warmer and drier). This is largely driven by the fact that 63% of national park area is in Alaska (!), with most of the rest in the Western US (see Figure 2). This shows the need for parks to be actively planning how to respond to climate change, and is a useful reminder that protected areas are not protected from climate change.

Renzi et al. argues that to successfully restore coastal wetlands, reducing stress & competition isn’t enough. To make restoration more effective at replicating intact habitat we should incorporate ‘positive species interactions’ (where one or both organisms benefits from the other without being harmed, aka ‘symbiosis’ in lay terms but in ecology symbiosis has a broader meaning). Examples include clumps of seagrass helping each other by capturing more nutrients and reducing erosion, or sponges on mangrove roots exchanging nutrients and carbon so both grow faster (See Fig 1 & 2 for more examples). Key recommendations are :to clump (not evenly space) plantings of seagrass or mangroves (in most but not all cases, context is important),  introduce a diverse set of plants and animals (rather than hoping for colonization later), and consider proximity to other wetlands.

Guest reviews from Steve Wood:

Many environmental groups have focused on using natural ecosystems to drawdown carbon dioxide to achieve climate goals. Baldocchi & Penuelas 2019 walks through the science of how that drawdown works. They cover the mechanistic science of limits to plant fixation of carbon, but in an extremely accessible way. Although they write from a neutral perspective, there are hints of doubt that drawdown could be achieved at scale to have climate-relevant impacts.

Herbicide residues from widespread chemical weed management can have negative impacts on terrestrial and aquatic ecosystems. Combined with herbicide resistance and lack of innovation of new herbicides has led people from corporations to ecologists to advocate for ecological approaches to weed management. Barberi 2019 gives an overview of ecological weed management approaches, with a lens on sub-Saharan Africa. They focus specifically on practices to: reduce weed seedling emergence; improve crop competitiveness; and reduce weed seedbank size. There is a particular emphasis on Striga management. This is a very thorough literature survey and would be a great entry point to understanding the literature. They do not, however, quantitatively synthesize the literature through tools like formal meta-analysis to put numbers to the impact of practices.

Baldocchi, D., & Peñuelas, J. (2019). The physics and ecology of mining carbon dioxide from the atmosphere by ecosystems. Global Change Biology, 25(4), 1191–1197.

Bàrberi, P. (2019). Ecological weed management in Sub-Saharan Africa: Prospects and implications on other agroecosystem services. In Advances in Agronomy (1st ed., Vol. 156).

Bogenschneider, K., Day, E., & Parrott, E. (2019). Revisiting theory on research use: Turning to policymakers for fresh insights. American Psychologist.

Burivalova, Z., Allnutt, T., Rademacher, D., Schlemm, A., Wilcove, D. S., & Butler, R. A. (2019). What works in tropical forest conservation, and what does not: Effectiveness of four strategies in terms of environmental, social, and economic outcomes. Conservation Science and Practice, in press(March), 1–15.

Cui, Y., Booth, D. B., Monschke, J., Gentzler, S., Roadifer, J., Greimann, B., & Cluer, B. (2016). Analyses of the erosion of fine sediment deposit for a large dam-removal project: an empirical approach. International Journal of River Basin Management, 15(1), 103–114.

Gonzalez, P., Wang, F., Notaro, M., Vimont, D. J., & Williams, J. W. (2018). Disproportionate magnitude of climate change in United States national parks. Environmental Research Letters, 13(10), 104001. Retrieved from

Grill, G., Lehner, B., Thieme, M., Geenen, B., Tickner, D., Antonelli, F., … Zarfl, C. (2019). Mapping the world’s free-flowing rivers. Nature, 569(7755), 215–221.

Renzi, J. J., He, Q., & Silliman, B. R. (2019). Harnessing Positive Species Interactions to Enhance Coastal Wetland Restoration. Frontiers in Ecology and Evolution, 7(April), 1–14.

White, E. M., Lindberg, K., Davis, E. J., & Spies, T. A. (2019). Use of Science and Modeling by Practitioners in Landscape-Scale Management Decisions. Journal of Forestry, 117(3), 267–279.



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

Monday, June 3, 2019

June 2019 science journal article summary

Butterfly on milkweed

I'm still not doing great with having a coherent theme; this month includes articles on biodiversity, remote sensing, dams, and coastal wetlands. The picture above is the first butterfly I've seen in my butterfly garden this year, eating from the first milkweed flower to open. After reading Sánchez-Bayo & Wyckhuys you may want to plant some too! If you know someone who wants to sign up to receive these summaries, they can do so at

The U.N.'s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) released a summary of a major report in May describing global biodiversity loss and extinctions (Diaz et al. 2019). The short version is "nature is in trouble, and so are we as a result." The most reported estimate is that about 1 million species face extinction (many within decades) unless we act to prevent that. I'd recommend looking at the policy summary and at least reading the bold headlines to get a bit more of the key findings. A few others worth highlighting include: declines in crop and livestock diversity is undermining agricultural resilience, drivers of change in nature (e.g. land use, direct exploitation, climate change, pollution, and invasives) are accelerating, goals like the Aichi Biodiversity Target and the 2030 Agenda for Sustainable Development cannot be met without major transformative changes (changes which are possible, albeit challenging), the parts of the world where declining nature is expected to hit people the hardest tend to be poor and/or indigenous communities, international cooperation to build a more sustainable global economy will be key to solve this problem, addressing the sustainability of food will also be important, and land-based climate solutions (e.g. bioenergy plantations and afforestation) have some tradeoffs. Many of these are obvious; the summaries under each headline often include useful detail, but there's too much to summarize at this level. So skim through and dive into the topics that pique your interest.
Sanchez-Bayo & Wyckhuys 2019 looks across 73 studies of insect decline from cross the world, and look at the drivers and other commonalities. A key limit of the paper is that they excluded any study that did NOT show a chance in abundance or diversity, so it's utility is limited to explaining declines where they have happened (see section 4.1). The take-away is that habitat loss seems to be the primary driver (~50% of declines), followed by 'pollution' (~26%, mostly pesticides and fertilizer), then disease and invasive species (18%) and climate change (7%). That means a sole focus on pesticides will miss key drivers of the problem. Figure 3 has a breakdown by taxonomic order, highlighting that dung beetles are in real trouble.

Raber and Schill 2019 is a methods paper describing their use of a cheap (<$5k) floating semi-autonomous drone to capture mm-scale 3D imagery of shallow coral reefs. The idea is to be able to track fine scale changes over time in coral more cheaply and accurately than using divers. They note that GPS accuracy was a problem but since the paper was written the authors have added a low cost RTK GPS at the nearest coast to solve that. The paper has lots of detail for anyone interested in trying it.

Pettorelli et al. 2018 is an overview of remote sensing of ecosystem functions (as opposed to the more commonly measured structure and composition). It's a good read, but for most people I'd recommend skipping to table 3 for an overview of existing sensors and data products that can map proxies of ecosystem function, and table 4 for some new and upcoming sensors and products.

Ezcurra et al. 2019 looks at how dams impact sediment transport in tropical estuaries, by comparing two undammed rivers to two dammed ones (see Fig 2 & 3 for a visual summary). They found that the coastal erosion due to dams leads to environmental impacts (fisheries decline, lost coastal protection, GHG emissions from eroded sediment, biodiversity loss) that may exceed the benefits of hydroelectric production on avoided GHG emissions. However, several assumptions in the paper are problematic (e.g. all eroded sediment is lost to the atmosphere as CO2 or methane), and likely pull towards overestimating the impacts. I'd focus more on the coastal changes than the potential implications.

Rogers et al. 2019 finds that coastal wetlands experiencing relative sea level rise (via either sea level rise or subsiding sea floor, or even sediment compaction and decomposition) sequester and store more soil carbon. They looked at relative levels over the last 6,000 years and how it related to soil carbon at different depths, as well as a site in Australia where there was rapid relative sea level rise in the last few decades. Their explanation is that as sediment accumulates, without relative sea level rise, the space available for vegetation shrinks, and thus organic sediment accumulates more slowly.

Ezcurra, E., Barrios, E., Ezcurra, P., Ezcurra, A., Vanderplank, S., Vidal, O., … Aburto-Oropeza, O. (2019). A natural experiment reveals the impact of hydroelectric dams on the estuaries of tropical rivers. Science Advances, 5(3), eaau9875.

Díaz, S., Settele, J., Brondízio, E., Ngo, H. T., Guèze, M., Agard, J., … Zayes, C. (2019). Summary for policymakers of the global assessment report on biodiversity and ecosystem services-unedited advance version. Retrieved from

Pettorelli, N., Schulte to Bühne, H., Tulloch, A., Dubois, G., Macinnis-Ng, C., Queirós, A. M., … Nicholson, E. (2018). Satellite remote sensing of ecosystem functions: opportunities, challenges and way forward. Remote Sensing in Ecology and Conservation, 4(2), 71–93.

Raber, & Schill. (2019). Reef Rover: A Low-Cost Small Autonomous Unmanned Surface Vehicle (USV) for Mapping and Monitoring Coral Reefs. Drones, 3(2), 38.

Rogers, K., Kelleway, J. J., Saintilan, N., Megonigal, J. P., Adams, J. B., Holmquist, J. R., … Woodroffe, C. D. (2019). Wetland carbon storage controlled by millennial-scale variation in relative sea-level rise. Nature, 567(7746), 91–95.

Sánchez-Bayo, F., & Wyckhuys, K. A. G. (2019). Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, 232(January), 8–27.

Friday, May 24, 2019

New book chapter (from CUP) available on agricultural metrics & corporate sustainability

Once upon a time (late 2013 or early 2014) I was asked to co-write a chapter on sustainable agriculture metrics with Peter Kareiva. I learned a lot writing it, and when I realized it would take a while to get published I wrote a blog post about the most surprising thing I learned (that global agricultural land had been decreasing since 1998, not rapidly expanding):

That surprise, and the blowback I got after publishing it, inspired me to write another book chapter which came out in late 2017:
and a follow-up blog since my writing wasn't clear enough:

But now, 5+ years later, the actual original book is finally published!

Those interested can read the final chapter at

The first half is OK but is out of date and was written when I knew far less about agriculture. I'd skip to the 2nd half (start with the "Can Corporate Sustainability reporting be a force for improved agricultural practices?" section). There's some interesting content I haven't seen anywhere else on corporate sustainabiltiy and food labels.

I haven't read the rest of the book yet but am looking forward to it! You can get the whole book here:  Agricultural Resilience: Perspectives from Ecology and Economics (Cambridge University Press)

Friday, May 3, 2019

May 2019 science journal article summary

Pretty flower

Merry May!

This month's summary is a bit of a grab bag as I settle into my new job and am reading a wide variety of topics.

I'm very happy to report that after about 5 years, a book I contributed a chapter to is finally published! The chapter is "Using environmental metrics to promote sustainability and resilience in agriculture" (co-authored by Peter Kareiva) and it's in "Agricultural Resilience: Perspectives from Ecology and Economics" from Cambridge University Press:

Unfortunately I wrote it when I knew far less about agriculture (and how to write well), so I can't entirely recommend it (especially all the specific metrics). But it has some useful content. The section "Food labels and sustainability" is still unique as far as I know in providing a concise (2 page) summary of research around food labels and consumer preferences around sustainability (although there are more comprehensive resources, e.g. "The Green Bundle" by Magali Delmas and David Colgan). The corporate sustainability information is badly dated but a decent primer for folks new to the field. Anyway, you can read my chapter here if interested: or buy the book from the link above. I haven't seen any of the other chapters yet but hopefully given the long wait they're all fantastic!

Also, normally when I find a paper not as useful as I hoped I don't review it. This month I'm including a couple that I'd normally skip since it may also be useful to see limitations flagged for papers which may be used to overstate a case.

To sign up to receive these summaries, visit

Anderson et al. 2019 argues that while investing in natural climate solutions (aka NCS, e.g. trees) is important to mitigate climate change, cuts to emissions from energy and industry are also urgent and imperative. As they put it, it's not "either/or" but "yes, and." Their key point is that while NCS offer many benefits, delaying emissions reductions from energy and industry by even a few years can add up to more than offset the reductions from NCS. They close by calling for conservationists to ensure that NCS mitigation is optimized, while also amplifying the need to work on complementary solutions to reduce anthropogenic emissions at their source.

Dinerstein et al. 2019 is a new spin on an older 'half earth' idea. They outline a "global deal for nature:" an ambitious plan for new protected areas and "other effective area-based conservation measures" (OECMs) which could include indigenous reserves and well-managed grazing areas. By 2030 they seek 30% of earth to be formally protected (currently we're at 15%) plus 20% more as 'climate stabilization areas.' The goal would be to minimize climate change and species extinctions via a companion to the Paris agreement, since preventing habitat loss and maintaining connectivity is much easier and cheaper than restoration after the fact. The paper is useful in identifying key areas for protection and potential policy mechanisms to consider. But Table 3 makes it clear that this is a wish list of several big policies that the environmental movement has been unable to achieve, without a plausible path to galvanize new support and/or come up with creative solutions beyond keeping humans out of most of the planet.

Searchinger et al. 2018 is an attempt to calculate the "carbon opportunity cost" of different ag land uses and habitats. Unfortunately, the assumptions taken together make this paper not very useful. For example, the idea that if food is not produced somewhere it simply will be produced elsewhere with global average values is a big stretch, but it's even more of a stretch to assume that intensifying production in one place will lead to land sparing elsewhere.

Dickson  et al. 2019 is an overview of how electrical "circuit theory" has been incorporated into the science of wildlife connectivity (mostly through an open source tool called circuitscape). Some key advances: recognizing that wildlife don't typically know and use a single optimal path, identifying pinch points that limit flow, and better explaining genetic patterns across a landscape. However, for animals with better knowledge of their landscape (e.g. seasonally migrating ungulates), circuit theory does not perform as well. They close with a quick summary of other applications in groundwater and fire. Check out figure 3 for a great example of how to make a basic bar chart fun and accessible.

Armitage and Fourqurean 2016 looked at how nutrient availability (both historic and manipulated) impacted seagrass biomass and soil organic carbon (SOC). Sites with a history of lower nutrient availability had lower soil SOC and much lower biomass (both above-ground and below-ground). Adding nutrients boosted above-ground biomass (especially P in nutrient-poor sites, with a smaller effect of N in moderate-nutrient sites), but below-ground biomass didn't respond as consistently. In fact, more sites lost below-ground biomass with extra P than gained it (the abstract misstates the findings). While it would have taken a longer study to accurately detect SOC changes due to biomass inputs, it actually went down with P addition. The authors hypothesize that the extra above-ground biomass from fertilization could trap more sediment and lead to higher SOC, which is plausible, but would have to be tested by a future study (as well as checking for impacts on N2O that could offset the C gains).

Kovacs et al. 2018 mapped seagrass in Australia (in clear shallow waters, ideal conditions) using four satellite sensors with pixel size from 30m to 2m. The results are surprising - overall all sensors had similar overall accuracy for both species ID and % cover. As expected, higher resolution  made it possible to see more detail (Figure 2 is great to compare sensors), but since it wasn't more accurate that would only be relevant if fine-scale distribution patterns were of special interest. Otherwise sticking with the coarser data would save time and money for mapping.

Two new lidar satellites were launched recently: ICESat-2 launched in Sep 2018 and GEDI in Dec (initial GEDI data should be released in June, ICESat-2 hasn't announced a date yet). While GEDI is more focused on measuring forest canopy height, ICESat-2 is also mapping vegetation (in addition to ice sheets, clouds, land surface, and more). GEDI will focus on middle latitudes, and ICESat-2 on the poles. Having these data available globally will be a big deal, especially for estimating forest carbon. For more on ICESat-2, Neuenschwander and Pitts 2019 has details on one of the planned data products (ATL08) which maps both ground surface and tree canopies. It's a dense paper, but Figures 4 & 8 are useful to get a sense of the output (they used simulated data), and the discussion has several useful details. The raw data is grouped into 100m cells to have enough photons per cell, but another data product (ATL03) maps each photon individually and can be used to investigate patterns within each 100m cell. Note that tree canopy height is consistently underestimated by ATL08.

Sun et al. 2018 argues that countries that import crops may also create local pollution problems, contrary to the usual thought that importing food shifts the environmental burden to the exporting country. Their case study shows that as China started importing more soy and growing other crops domestically, their nitrogen overuse increased. However, that doesn't make a strong general case for their assertion, and while China could certainly benefit from more soy rotation, fertilizer overuse there is driven by a series of political and cultural factors that again make it hard to generalize.

Anderson, C. M., DeFries, R. S., Litterman, R., Matson, P. A., Nepstad, D. C., Pacala, S., … Field, C. B. (2019). Natural climate solutions are not enough. Science, 363(6430), 933–934.  

Armitage, A. R., & Fourqurean, J. W. (2016). Carbon storage in seagrass soils: long-term nutrient history exceeds the effects of near-term nutrient enrichment. Biogeosciences, 13(1), 313–321.

Dickson, B. G., Albano, C. M., Anantharaman, R., Beier, P., Fargione, J., Graves, T. A., … Theobald, D. M. (2018). Circuit-theory applications to connectivity science and conservation. Conservation Biology, 33(2), 239–249.

Dinerstein, E., Vynne, C., Sala, E., Joshi, A. R., Fernando, S., Lovejoy, T. E., … Wikramanayake, E. (2019). A Global Deal For Nature: Guiding principles, milestones, and targets. Science Advances, 5(4).

Fisher, J.R.B. and Kareiva, P. 2019. Using environmental metrics to promote sustainability and resilience in agriculture. In Gardner et al. (Eds), Agricultural Resilience: Perspectives from Ecology and Economics. Cambridge University Press

Kovacs, E., Roelfsema, C., Lyons, M., Zhao, S., & Phinn, S. (2018). Seagrass habitat mapping: how do Landsat 8 OLI, Sentinel-2, ZY-3A, and Worldview-3 perform? Remote Sensing Letters, 9(7), 686–695.

Neuenschwander, A., & Pitts, K. (2019). The ATL08 land and vegetation product for the ICESat-2 Mission. Remote Sensing of Environment, 221 (April 2018), 247–259.

Searchinger, T. D., Wirsenius, S., Beringer, T., & Dumas, P. (2018). Assessing the efficiency of changes in land use for mitigating climate change. Nature, 564(7735), 249–253.

Sun, J., Mooney, H., Wu, W., Tang, H., Tong, Y., Xu, Z., … Liu, J. (2018). Importing food damages domestic environment: Evidence from global soybean trade. Proceedings of the National Academy of Sciences, 115(21), 5415–5419.



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

Monday, April 1, 2019

April 2019 science journal article summary

Tomato seedlings

Happy Spring!

Since I've just changed jobs I asked for help in putting this summary together; Steve Wood from The Nature Conservancy kindly reviewed four of the articles below. Also, these summaries come from me (and Steve in this case) and do not reflect the views of our employers or any other organization. Any mistakes are my own.

If you know someone who wants to sign up to receive these summaries, they can do so at, for folks interested in science communications, I've been getting a lot of good ideas from the short daily emails Bob Lalasz (from Science + Story) sends. You can check out a few examples at and if interested sign up at

Tack et al. 2019 identifies priority areas to focus land protection on the most important wildlife corridors used by pronghorn and greater sage grouse in the Northern Great Plains, specifically north-central Montana into southern Saskatchewan. Sage grouse in this area depend on migration, as do about half of the pronghorn population. Private lands in the area are roughly half ranches on native sagebrush, and half cropland (with public land typically primarily used for cattle grazing). Cropland expansion is the main driver of habitat loss (followed by energy development), and protected areas only cover ~5% of pathways for both species. So priorities for protection are on lands used for migration with a higher chance of cultivation. Note Figure 4 which shows the importance of unprotected public, private, and even cultivated land. Fences impede migration, but marking them with flags reduces collisions.

McGill et al. 2018 modeled greenhouse gases (GHGs) of groundwater-irrigated vs rainfed croplands in the Midwest US. Irrigated fields had higher net GHGs (27 g CO2e/m2/yr) than rainfed (a net sink, -14g CO2e/m2/yr), mainly due to higher N2O emissions and fossil fuel use to pump groundwater. However, since irrigation also increased yield the emissions per unit of crop yield were similar: 0.04 kg CO2e/ kg yield for irrigated vs -0.03 kg CO2e/ kg yield for rainfed (again a GHG sink). Finding the rainfed system to be a net GHGS sink is surprising and unusual, even if you assume that no-till farms have net C sequestration (which is unlikely). There are some other odd findings like fertilization reducing soil C. But the overall idea should be valid: irrigation will generally lead to wetter soil (w/ higher N2O emissions more than offsetting higher soil C) plus energy use to pump water.

Smith et al. 2019 is a review of the environmental impact widespread adoption of the voluntary Bonsucro standard for sugar cane could have. They find impressive potential, especially if efforts are targeted well and involve compliance with all standards and criteria. Half of global environmental potential benefits could be met with only 10% of total production area (check out figure 4 for details). However there are several challenges, including what to do with farms totally unable to meet those standards (e.g. large areas in India). This paper also models impact IF all participating farms actually met all target outcomes, and doesn't look at how companies could drive that or what would be practical with different levels of investment. Nonetheless, this shows a lot of potential especially if we can move beyond practice based frameworks to those that are outcome-based and carefully targeted. You can read a blog about this work here:
Han et al. 2018 is a meta-analysis of 68 studies of how straw incorporation affected carbon sequestration and crop yields across China. On average it sequestered 0.35 t C / ha / yr in the upper 20 cm of soil, and boosted crop yields 13%. It worked best on clay soils, high crop intensities, and in areas where soil is currently being degraded (NE China).

Have questions about the four papers below? Contact Steve at stephen.wood@TNC.ORG.

Soil health has become a major are of interest, but there is uncertainty about how to measure and define it. Derner et al. 2018 tackle the question of how to define soil health for grazing lands. This is an important task because the notion of soil health emerged from row-crop agriculture, yet the way grazing lands are managed and the environmental services they provide are starkly different to row crop agriculture.
The authors argue that a soil health approach to grazing lands should re-focus grazing management on managing for ecosystem processes, rather than maximizing short-term profit. And this requires building cross-institutional capacity and training, adaptive management, and long-term monitoring. The authors argue against adoption of a single set of practices or indicators. For instance, a soil health indicator from row crop agriculture is high soil cover, but in grazing systems high amounts of bare ground can be necessary for some grassland bird species. This paper is also noteworthy for the mix of authors--everything from university professor to rancher.

The two papers by Unks et al. 2019 aim to understand the drivers of pastoralist livelihood vulnerability in one of the Northern Rangeland Trust community conservancies. They argue that the rangeland institutions in central Kenya going back to the colonial era have promoted formal land tenure, whether at the individual or community level. But, because forage production is patchy, successful grazing requires a high level of mobility to access resources in different areas at different times. This type of management is at odds with formal property regimes, as well as at odds with realities of modern life, like employment at conservancy lodges and keeping children in school. Herders now face limited mobility, which means that livestock husbandry has shifted towards browsers, like goats and camels, which do better on lands with low grass productivity. Limited mobility also has made livestock husbandry more individualistic, leading to greater inequality among households. Greater inequality leads to unequal ability to cope with future climate change.

The papers offer nuanced insight into the drivers of change and livelihood vulnerability. The narrative promoted by conservation non-profits tends to be more simplistic: poor current management--stocking rates, population growth--is the main driver of poor vegetation and livelihoods. By showing the importance of long-standing institutional, climatic, and socio-economic change, the authors imply that land-tenure-based management plans (like those promoted at NRT) will not fix the ecological or livelihood challenges. In bringing more nuance they highlight greater challenges, but they don’t offer insight into what solutions to those greater challenges might be.

Finally, Rosenzweig et al. 2018 focuses on quantifying whether it is possible to lower fertilizer and herbicide use while maintaining yields via changing crop rotations. The focus is on dryland, no-till wheat in Colorado and Nebraska. They tested three groups of cropping systems, all of which had wheat in the winter. In the summer they differed by: (1) natural fallow one out of two years;  (2) a summer crop (corn, sorghum, millet, peas, or sunflowers) replacing fallow every couple of years; (3) continuous cropping with mixtures of the same crops from (2). They showed that the continuous cropping system had the highest nutrient retention, greater fungal colonization of roots (which increases nutrient retention), lowest herbicide use, lowest yield penalty, and highest profitability. Continuous cultivation had greater net revenue than basic fallow by $100 per hectare per year.

One reason I like this paper is that it challenges the idea that continuous cultivation is inherently bad and that natural fallow/regeneration is good. The paper shows that planning cropping and restoration is likely the key to ecological intensification. One limitation of this study is that because there were multiple crop combinations in each of the categories tested that it’s not possible to discern which of those combinations had the greatest effect.

Derner, J. D., Smart, A. J., Toombs, T. P., Larsen, D., McCulley, R. L., Goodwin, J., et al. (2018). Soil Health as a Transformational Change Agent for US Grazing Lands Management. Rangeland Ecology & Management, 71(4), 403–408.

Han, X., Xu, C., Dungait, J. A. J., Bol, R., Wang, X., Wu, W., & Meng, F. (2018). Straw incorporation increases crop yield and soil organic carbon sequestration but varies under different natural conditions and farming practices in China: a system analysis. Biogeosciences, 15(7), 1933–1946.

McGill, B. M., Hamilton, S. K., Millar, N., & Robertson, G. P. (2018). The greenhouse gas cost of agricultural intensification with groundwater irrigation in a Midwest U.S. row cropping system. Global Change Biology, 24(12), 5948–5960.

Rosenzweig, S. T., Stromberger, M. E., & Schipanski, M. E. (2018). Intensified dryland crop rotations support greater grain production with fewer inputs. Agriculture, Ecosystems and Environment, 264, 63–72.

Smith, W. K., Nelson, E., Johnson, J. A., Polasky, S., Milder, J. C., Gerber, J. S., … Siebert, S. (2019). Voluntary sustainability standards could significantly reduce detrimental impacts of global agriculture. Proceedings of the National Academy of Sciences, 116(6), 2130–2137.

Tack, J. D., Jakes, A. F., Jones, P. F., Smith, J. T., Newton, R. E., Martin, B. H., … Naugle, D. E. (2019). Beyond protected areas: private lands and public policy anchor intact pathways for multi-species wildlife migration. Biological Conservation, 234, 18–27.

Unks, R. R., King, E. G., German, L. A., Wachira, N. P., & Nelson, D. R. (2019). Unevenness in scale mismatches: Institutional change, pastoralist livelihoods, and herding ecology in Laikipia, Kenya. Geoforum, 99, 74–87.

Unks, R. R., King, E. G., Nelson, D. R., Wachira, N. P., & German, L. A. (2019). Constraints, multiple stressors, and stratified adaptation: Pastoralist livelihood vulnerability in a semi-arid wildlife conservation context in Central Kenya. Global Environmental Change, 54, 124–134.



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

Friday, March 1, 2019

Transition for monthly science updates


As many of you have heard, this is my last day at The Nature Conservancy; I'll be taking a new job at The Pew Charitable Trusts on their conservation science team. I don't know yet what will happen with these summaries but don't despair! I hope to keep them going in some form - likely with a different topical focus. If you know someone who is feeling lucky and wants to sign up to receive these summaries despite the uncertainty, they can do so at

I've been frantically wrapping up work so have read less science than usual this month. But I did write a blog post explaining why seemingly silly questions like how to define forests and deforestation are actually both tricky and really important: How many trees make a forest? I talk about The Accountability Framework and the critical role it can play in helping to end deforestation:

The only papers I reviewed this month are one about how scientists read scientific literature, and two soil papers (from TNC's Deborah Bossio and Steve Wood) which are both summarized on this blog:

Colleagues working in applied conservation often tell me they have no time to read scientific literature. Tenopir et al. 2015 is an article about how faculty in five US universities seek out scholarly literature (including but not limited to the sciences)! I'll be honest - I skimmed this looking for two bits of information: scientists reported reading an average of 26 articles per month (Fig 1), and spent 32 minutes on each article (Fig 2). I read fewer articles, and usually read them faster. But even these academics are spending less than two days out of the month on this. Surely most of us can find a few hours! There are some other interesting tidbits here. Almost 2/3 of articles read are from the last two years - so have a good comms plan for your research! Also, NONE of the surveyed scientists read articles on a mobile device like a tablet, which is a huge missed opportunity for those long commutes on mass transit!

Soil organic carbon (SOC) is often claimed to improve crop yields.  Oldfield et al. 2019 tests that claim with a global meta-analysis of maize and wheat. They find higher SOC is associated with higher yields, up to ~2% SOC. They then look at the ~2/3 of global maize and wheat lands below 2% to estimate the opportunity to improve yield by boosting those soils to 2% SOC. Globally they estimate that we could produce ~5% more maize and ~10% more wheat, which represents 32% of the global yield gap for maize (largely in the US), and 60% for wheat (largely in China). Check out Figure 4 for global opportunity maps. Note that there is a lot of variance in the data, and it's even possible yields could decline slightly as SOC increases.

Vermeulen et al. 2019 is a call to action on improving global soil carbon stocks. It reviews some of the challenges that have impeded action at scale,and emerging opportunities that could give soil initiatives a boost. They call out three key needs, and look at possible actions to advance all three. First, a compelling vision for action led by political champions. Second, a stronger business case (including evidence of success for both public and private investors). Finally: a more compelling value proposition for farmers and land managers. They also highlight the need for practical measurement protocols, and several policy gaps. It's a quick read at 3 pages so worth a look.

Oldfield, E. E., Bradford, M. A., & Wood, S. A. (2019). Global meta-analysis of the relationship between soil organic matter and crop yields. SOIL, 5, 13–32.

Tenopir, C., King, D. W., Christian, L., & Volentine, R. (2015). Scholarly article seeking, reading, and use: A continuing evolution from print to electronic in the sciences and social sciences. Learned Publishing, 28(2), 93–105.

Vermeulen, S., Bossio, D., Lehmann, J., Luu, P., Paustian, K., Webb, C., … Warnken, M. (2019). A global agenda for collective action on soil carbon. Nature Sustainability, 2(1), 2–4.



p.s. as a reminder, you can search all of the science articles written by TNC staff (that we know of) here
(as you publish please email to help keep this resource current). This will be my last plug for this resource since I'm leaving TNC.
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

Tuesday, February 26, 2019

Tips for being a more effective scientist

After 13 years as some form of scientist at The Nature Conservancy (TNC), I’ve learned a lot. Here are a few of my top lessons learned that are easy to miss when you’re focused on your core responsibilities. There are many ways to be a successful applied scientist; please share your own advice in the comments about what you have learned that I left out. Also, I recognize that these all take time and can add work. So don't be afraid to say no to requests to free up time to do things like this that you may not get asked to do! 

1. Always make time to learn
Knowledge is the primary currency of scientists. If you don’t make time for learning, you’re withdrawing on an account that won’t replenish. Dedicating even a small amount of time to learning is essential to staying effective. I spend ~1-2% of my time reading scientific literature: enough to get through several papers each month and summarize them. I also spend a few percent working on diversity & inclusion issues at TNC, which has helped me learn on completely different topics. Hate reading papers? Call trusted colleagues to pick their brains, attend a webinar, or take a training on something you’re bad at. I was terrible at written and spoken communications, as well as conflict management, when I started at TNC. I’ve improved a lot by putting in effort. Don’t have time? Read papers on planes, trains, and buses (I do this on a tablet synced to Box), while eating breakfast, or when you need a break from email and talking to people. Pick a couple of your least productive standing meetings, switch from 60 to 30 minutes (or cancel), and use the time saved for learning.

      2. Don’t be afraid to speak up for science and rigor
Scientists need to advocate for the use of evidence in making decisions. That can at times mean pushing for measures, providing internal critique and suggestions to statements by colleagues who aren’t as current with the science, and in general helping to ensure your organization is well aligned with good science. That can be uncomfortable, and many of us are reluctant to speak up. But I find that most of the time, when I raise concerns thoughtfully and back them up with science, people I work with have appreciated it (even when I disagree with them). I’ve even had senior managers complain to me that people are too reluctant to push back on them sometimes!

      3. Step up to solve problems when you can
You likely sometimes run into a problem that you know has a relatively simple fix but which is not your job. Consider stepping up to fix it anyway. There have been several times when I’ve been annoyed by (and affected by) a problem and realized that I could make a big dent in it with just a few days of work. People see this as leadership, and it pays off. Examples could include working with a colleague in IT to rapidly put together a simple information system or web page; helping to organize or connect scientists on a topic who are currently not talking to each other; engaging with Employee Resource Groups on projects to improve diversity, equity or inclusion; or doing whatever else inspires you. Always thank the people who go out of their way to help you on these projects – a little recognition and appreciation goes a long way.

      4. Network (internally and externally)
At a big NGO like TNC, there are guaranteed to be several staff who can help you learn and grow in your job (as well as be fun to work with). But, especially for field scientists, it can be hard to connect with others. Find out who works on your topic in other programs, and build a network of people you can ask to collaborate on papers, review your work, help brainstorm, etc. You can do it via Connect or Workplace, or via email and phone. 

This applies outside of your organization too, especially if you’re at a smaller one. Mentoring students at universities (e.g. via NatureNet) is one great way to do this – you build connections with both the student and their academic mentor. I’ve also found that authors of scientific papers are almost always thrilled to be contacted with questions or feedback. I also have a policy of making time (15-30 minutes) for anyone who wants to connect with me; you never know how you can help them and vice versa. That includes folks in non-scientific roles (e.g. admin or operations) – they play a critical role in getting things done and are sometimes brushed off by busy scientists when they have questions. It also means being an ally for people who need it. Finally, look for ways to get to know decision-makers! Sometimes I’ve been invited to a non-scientific event to represent TNC, gone resentfully, and walked away with invaluable contacts I didn’t expect.

      5. Learn your biases and reflect on them often
We all have bias and a perspective that informs how we do science. Many of us have strong opinions backed up by considerable reading and thought, so it can be hard to acknowledge that we almost always have bias, and that there’s a lot we don’t know. Pretending you can 'cure' bias means you'll likely be blind to it - focus on understanding it and mitigating it instead. 

I try very hard to follow advice from Ray Bradbury, which is that whenever I notice myself having an emotional reaction to something I’m reading, I pause and think about why I’m reacting. For example, if I’m reading a paper that contradicts what I think I know, I work extra hard to ask “How could this be right? What assumptions am I making? How could I reconcile conflicts between this information and other information I have?” Sometimes careful science lands you in the same place as your gut. But take the time to be sure, and disclose your leanings to colleagues so they can help to bring other perspectives that balance yours. 

Talk to people in other scientific camps, and listen to them in order to gather data, understand, and reflect (not to win an argument). Seek collaborators who disagree with you. This also includes listening to non-scientists who push back on recommendations by scientists about how much time and data we need to answer a challenging question! Most scientists prefer to answer questions with “it depends,” and sometimes we need to be pushed to provide actionable information or risk missing a chance to impact a decision.

      6. Pay attention to your colleagues’ style
While it’s obvious, the fact that others think and feel very differently from you is surprisingly non-intuitive to me. I remember working with a colleague years ago who was consistently making mistakes on a process, and I added more and more detail to the guidance to try and fix it. But for him (and many others), as guidance gets longer, they read less of it. I had to understand his style and adjust accordingly. Similarly, I like to resolve issues through rapid back and forth discussion, but others don’t think that way, and instead need materials in advance and then time to think before responding. The “interaction styles” training is very helpful for this, as is the Enneagram. Learning the styles of some key colleagues who I don’t intuitively understand has been critical for me to build relationships and work effectively. 

One final note - I found the photo in this post hilarious and used it for years at work (it was taken mid-dance at my wedding). But I learned that a couple of colleagues took it as a lack of seriousness or credibility, and once I learned it undermined my work with some people, I changed it. So pay attention to how some of your non-work choices impact your work, and reflect on when to bend (e.g. pick a more professional photo or username), and when to stick to your guns (I still haven't cut my hair).