Best of 2024 science summaries

Happy New Year,

How better to celebrate the new year than with old science?!

As usual, here are my favorite 15 reruns (article summaries) from 2024, plus a few of my favorite bits about AI since I keep getting requests for more of that:

• Don’t put anything sensitive into AI! Enterprise licenses provide some protection for non-public but not highly sensitive info.
• I loved these tips for better AI prompts to help you get better results: https://www.oneusefulthing.org/p/getting-started-with-ai-good-enough  
• This is a great overview of some really good and really bad use cases for AI: https://www.oneusefulthing.org/p/15-times-to-use-ai-and-5-not-to
• Remember that AI is always changing. As of mid-December, Google Gemini’s NotebookLM not only turns a PDF you upload into an NPR-style podcast, it also now lets you interact w/ the “hosts”!  

Upset at the articles I missed? Please email me your own favorites from 2024 and I'll do what I can to include them in upcoming summaries.

As always people can sign up to receive these summaries at http://bit.ly/sciencejon (no need to email me). On with the reruns!


CLIMATE CHANGE
OK, for years people have been hyping the potential of a kind of seaweed (Asparagopsis) to reduce methane emissions in cattle. But the in vitro evidence was mixed - with potential toxicity and downsides a concern if the dose wasn't just right. George et al 2024 is a live trial with good news! They found methane emissions from cattle given an Asparagopsis additive were cut roughly in half compared to control, with 6.6% higher weight gain per unit of feed and no substantial impacts on quality or health (fat color maybe a bit better, tenderness maybe a bit worse). The methane reduction peaked at day 21 and declined afterwards, but since most cattle are in feedlots only ~3 months (ranging from 1.5-4) the decline after day 100 is pretty moot. That's a lot of potential! The only potential downsides were ~50% higher bromine residues in kidney and muscle (I couldn't quickly find guidance on safe levels). Caveats: 1) there were no conflicts declared but the authors appear to almost all work as feedlot consultants and it's single rather than double-blinded, 2) in the US the feedlot phase is only about 15% of the lifecycle emissions of a cow (and of that, some is from growing crops and nitrous oxide) so TOTAL impact on CO2e / kg beef is not as dramatic. Overall my take is 1) this should absolutely be tested and replicated more - anything that reduces the very high carbon of beef is worth pursuing. BUT 2) if this is marketed as "green beef" or license to avoid reductions, it could be net harmful for the climate. and 3) IF spraying this solution on grass worked similarly and didn't inhibit development of calves, the impact could be much higher (since ~80%ish of a cow's life is grazing prior to feedlot, and methane emissions are higher on grass than feed). So let's test that too (note: there’s a new study claiming a ~1/3 reduction in methane during grazing via seaweed supplements that I haven’t reviewed yet). There's a blog about this at https://www.theguardian.com/australia-news/article/2024/aug/18/feeding-seaweed-supplement-to-cattle-halved-methane-emissions-in-australian-feedlot-study-finds

Trencher et al, 2024 is an analysis of the quality of carbon credits on the voluntary market. They focus on the 20 companies retiring the most credits between 2020-2023 (134 million metric tons CO2e), which is 20% of all global retirements on the three registries (see Fig 1 for company list). They found 87% of credits have a high risk of not providing real additional reductions (6% were low risk, most of the rest was medium), and 97% of credits focused on avoiding emissions rather than removal. Note that they classified all REDD+ (reducing deforestation and/or degradation) as high risk given that they have often 1) overestimated additionality, 2) not stopped deforestation, and/or 3) displaced deforestation elsewhere (aka 'leakage'). They also classify large-scale renewable energy as high-risk, since the price of credits is not typically the decisive factor in those projects (they are often built w/ or w/o credits) and they are often build in countries w strong government support for renewable energy. They also found that companies strongly prefer the cheapest credits (which creates demand for lower-quality offsets) often from older projects, although some companies have paid a lot more for REDD projects. The authors call for more regulation of the voluntary market, and for companies not using voluntary credits to support claims of offsetting emissions.

 
CONSERVATION IMPACT:
Langhammer et al. 2024 is the big splashy new Science paper looking at the global impact of conservation. It's a meta-analysis of trials comparing interventions to counterfactuals (similar areas w/o action). They found conservation helps 2/3 of the time (45% of trials led to absolute improvement in biodiversity, 21% reduced biodiversity loss), but is harmful 1/3 of the time (in 21% of trials biodiversity declined more due to conservation, in 12% it improved less due to conservation), and only 2% of trials showed no difference). That's not a great track record - I'd hoped net harm would be rare (1/3 is very high!), and just over half the time we're losing biodiversity despite trying to stop it. Fig 2 helpfully shows how impact varies by type of intervention: protected areas show the smallest positive effect on average, and invasive species removal shows the largest positive effect. I'd ignore "sustainable use of species" b/c it's a weirdly broad category that somehow only included 4 papers on wildlife hunting and 1 on fishing, although a few fishing papers are included under protected areas (details in the supplement - this makes me think their sample is not representative of conservation broadly). While the authors conclude conservation is working and we should do more of it, I bet if this was a paper on medical efficacy we'd consider interventions that are 2/3 helpful and 1/3 harmful an urgent cry to improve efficacy BEFORE we try to scale work that is so often ineffective or harmful. Would you send your kids to a school where 1/3 of students learned less than kids not in school at all?


EVIDENCE ASSESSMENTS / SCIENTIFIC REPRODUCIBILITY:
Scientists often complain policy makers don't follow our recommendations (or even read them). But Brisco et al. 2023 finds that recommendations from meta-analyses tend to change over time as research continues. They looked at 79 papers (121 meta-analyses) and found that over time 93% of analyses either had a big change in effect size (+- 50% or more, see Fig 2 for examples) or change in statistical significance (see Fig 3). The key results are in Fig 5, which I find pretty confusing. Results staying consistently statistically significant w/ each study is rare, and ~25% of analyses showed a reversal in effect (from positive to negative or vice versa). Those reversals are the change we care the most about since it means action can backfire. BUT if you ignore the studies that were never statistically significant (seems safe) it's only 12% of analyses that flip, and if you also ignore the ones that lost significance (meaning the reversal is less meaningful) it goes down to 11%. That's still pretty bad though - 1 time out of 9 the scientific recommendation might lead to the opposite outcome we intend. They recommend scientists use cumulative meta-analyses to look for trends, and the reminder that we're often wrong reinforces the need for adaptive management and an empirical approach to seeing what works in a given context.
 
 
FIRE:
Pivello et al. 2021 is a good comprehensive overview of wildfire across Brazil. It's long and dense so hard to summarize! Natural fires are most common at the beginning of the wet season when lightning ignites accumulated dry vegetation. Fig 1 has an overview of fire by biome: the Amazon followed by Cerrado have the most fires; the Pantanal and Cerrado typically have the highest % burned (they are both fire-dependent, as is the Pampas, see Fig 2), and in 2020 the Pantanal had roughly triple the % burned and fire density as others. Pollen evidence (from a different study, Power et al. 2016) indicates fire activity in the Pantanal peaked about 12,000 years ago (people have only lived there for about 8,000 years, and grazed cattle for ~250). Introducing cattle has caused a shift from burning every 3-6 years (mostly in the beginning or sometimes end of the wet season) to burning every year or two during a relatively dry part of the wet season (see Fig 6). Conversely, fire suppression in the Cerrado has also driven woody encroachment of savannas. In the Amazon and Atlantic Forest, natural fire is rare and very infrequent, making fire especially harmful as species are not adapted to it. The combination of deforestation and drought make it much easier for fire to spread (and Amazonian deforestation means more drought in the Pantanal). 1/3 of the forest in the Amazon from 2003-2019 were associated w/ deforestation. Indigenous people mostly used fires in small areas, but since European colonization it's used at larger scales to clear land permanently (or alternately suppressed, see Fig 7 for a nice timeline of fire landmarks). Integrated fire management (IFM) is uncommon (except a few federal protected areas, mostly in the Cerrado). Only Minas Gerais and Roraima states have IFM laws. The authors recommend: 1) fire management policy should include climate mitigation and poverty reduction to reduce fire risk; 2) better fire monitoring and management systems; 3) filling knowledge gaps around drivers of fire, how fire impacts wetlands, human dimensions of fire, impacts of different fire regimes on grazing productivity and carbon; 4) better enforcement of illegal fire use (including more resources); 5) including local communities in developing fire management plans, and 6) national and state level fire policies with adequate resources for implementation (including data collection and sharing, and clear and simple rules about fire use).
 
Balch et al. 2024 found that over the last 20 years fires in the US have been spreading faster. In the Western US over 20 years the average peak daily growth rate (the average of the fastest each fire grew on a given day) increased 2.5 times (in California they increased by 4 times). The fastest 3% of fires nationally (spreading more than 1,620 ha in a day) destroyed between 78-89% of the buildings lost to fire (the paper lists each number in different section for the same stat). I’ve heard a lot more about severity and frequency and extent of fire, but thinking about speed is also important as faster fires are harder to respond do, and may make really smooth coordination increasingly important. Increases in drought conditions and potential increases in high winds could make this worse over time. 


FRESHWATER:
Flitcroft et al. 2023 notes that counting effective freshwater protection globally is really hard (as is getting effective protection to happen). Fig 1 has a nice summary of how restrictive different protection mechanisms are. They also call for both better management of existing protected areas (PAs) to include freshwater conservation needs, and protections for freshwater in new places. While issues around data resolution and data availability continue to pose challenges to freshwater conservation, they argue that more explicit consideration of both freshwater and terrestrial objectives in any area-based protection is a good start.
 
Jasechko et al. 2024 is a global assessment of groundwater levels since 2000 (using 170,000 wells and 1,700 aquifers) and comparing them to earlier trends for ~1/3 of those aquifers. They found 36% of aquifers were drying up (water level dropping deeper by 0.1 m / yr or more), and 6% of aquifers were improving (water level rising 0.1 m / yr or more), w/ 58% of aquifers not changing quickly in this century. 30% of the aquifers where they had 40 years of data declined faster in the 21st century than the 20 years prior (see Fig 3), but in 49% of those aquifers declines slowed or reversed. Unsurprisingly the trend is worst in drylands w/ farmland, and groundwater deepening is globally correlated w/ low precipitation, high evapotranspiration, and extent of agriculture. See Fig 1 and 2 for global map of trends, highlighting hotspots of decline in CA, the US high plains, Iran, India, central Chile, and a few others. There's a news article about the study at https://www.cnn.com/2024/01/24/climate/groundwater-global-study-scn/index.html

Wang et al. 2024 looks at how climate change has changed the seasonality of river flow (how much it varies month to month, including frequency of droughts and floods). They found that ~14% of long-term river gauges show changes in seasonality over the last 50 years that isn't driven by changing annual precipitation. The surprise is that seasonality is mostly DECREASING counter to the narrative of more floods and droughts (see Fig 1 for a map of results, and Fig 2 which adds detail). In their figures brown means less seasonality (more even flow): "L+" means low flows become higher flows (NOT higher frequency of drought) while "H-" means floods see lower flood volume (again NOT lower frequency of flood events). You'll see most of North America, most of Europe, and some of Russia have seen reduced seasonality in recent decades. Blue means MORE seasonality, focused in: SE Brazil, some European countries, and in the US the SE and some of the Rocky Mountains. The explanation is worth reading in full, but in brief: 1) snow melting earlier means less runoff from snow at the same time as spring rains, 2) early spring greening means more water gets transpired, 3) it's more complicated in places not dominated by snowmelt.
 

HORIZON SCANNING / EMERGING ISSUES:
I realized I've only rarely reviewed Bill Sutherland's annual "horizon scan" article listing 15 emerging conservation issues that potentially deserve to be better-known. Last year (I just read the 2024 version a year late) they used artificial intelligence to generate some of the ideas but none made the cut. Here's the final list so you can decide if any are worth looking up (and here’s the brand new 2025 paper if you want to catch up):
1. New sources of hydrogen for energy (mining or electrolysis instead of natural gas),
2. Decarbonized ammonia (making fertilizer w/ lower carbon emissions but could increase fertilizer wasted),
3. Feeding people and/or animals w/ cultivated bacteria,
4. Light-free artificial photosynthesis (yes, it's as weird as it sounds) for indoor ag,
5. Enhanced rock weathering at scale (putting rock dust on croplands to sequester carbon),
6. Potential global declines in earthworm populations (more data is needed to see if UK decline is representative),
7. Ecoacoustics to monitor soil ecology (testing how meaningful soil sounds are for estimating things like biodiversity and water flow),
8. Wildfire affecting El Niño and La Niña phase (aerosols leading to the La Niña phase),
9. Benchtop DNA printers (potential to eventually allow guerilla genetic engineering),
10. Better predicting chemical toxicity from early data,
11. a skyscraper city planned in Saudi Arabia that birds could crash into when migrating from Europe to Africa.,
12. Sea urchin die-offs (possibly from disease) leading to algal overgrowth on corals and other marine ecosystems,
13. Ocean-based carbon removal (from the air or dissolved in water to stable forms),
14. Warming "twilight zones" (200-1000m below sea surface) affecting global nutrient and carbon cycles, and
15. Melting Antarctic ice changing deep sea currents.


MAMMALS:
Greenspoon et. al 2023 is an attempt to estimate the biomass of all wild mammals on earth (combined), arriving at 60 Mt total: 20 Mt (million metric tons) on land (half from "even-hoofed" mammals, see FIg 2), and 40 Mt in oceans (23 Mt of which comes from baleen whales). But the kicker is that they estimate human biomass at 390 Mt, and livestock biomass at 630 Mt (420 Mt from cattle: which is more than all humans plus all wild land mammals). Fig 4 awkwardly tries to compare all mammal biomass on earth, showing how wild species have been squeezed. The wild mammal estimates mostly come from the IUCN red list which skews towards expert assessments of more threatened spp., and the numbers won't be "right" for several reasons (these estimates are hard, and the data are highly limiting). But it seems solid that humans and livestock substantially outweigh wild mammals.
There's a good critique of the paper (arguing that Greenspoon et al. underestimate biomass by a factor of 5.5) by Santini et al. here https://www.pnas.org/doi/10.1073/pnas.2308958121 and a reply from the Greenspoon authors pointing out why the methods used in the critique are also (differently) flawed: https://www.pnas.org/doi/10.1073/pnas.2316314121
 

MIGRATORY SPECIES / WILDLIFE CONNECTIVITY:
The new State of the World's Migratory Species report (UNEP-WCMC 2024) has an update on how the 1,189 migratory species in CMS are doing. Almost half (44%) are in decline (with 22% at risk of extinction, including 97% of listed fish spp), 1/3 are stable, and the rest are split between improving and unknown. The report also notes that 399 spp not even listed in CMS (including ~200 fish spp, ~150 bird spp, and ) are at risk (from critically endangered to near threatened). See Fig 2.10b for an overview of which migratory species CMS leaves out (including horseshoe crabs!) and 2.10c for the subset at risk. Unsurprisingly the main threats are habitat loss (along w/ degradation and fragmentation) and overexploitation (hunting and fishing). Recommendations on page ix-xi are familiar and unsurprising (albeit important). There's a blog about this paper with key highlights at: https://www.unep.org/news-and-stories/press-release/landmark-un-report-worlds-migratory-species-animals-are-decline-and
 
Littlefield et al. 2024 (I'm a minor author) examines how wildlife road crossings can be beneficial to help species adapt to climate change. We recommend that when siting crossings we should consider a) current wildlife movements, AND expected short-term and long-term shifts in species range and migrations due to b) climate change AND c) human land use change (expansion of housing, ag, etc.). We show how doing this was accomplished for elk in Colorado.
For this to work well, diversion fencing is important to channel wildlife to crossings, and avoiding future fragmentation is key. The paper is open access. There's a press release for the paper here: https://fish.freeshell.org/publications/Littlefield2024-PressRelease.pdf


POLLINATORS:
Li et al. 2024 is a methods paper about using land cover data to predict floral resource availability for pollinators. I'm an author despite minimal input; the lead author based this on work by the last author, who I provided some guidance to when he was a postdoc. There are a few potentially interesting things in here. 1) Most pollinators don't make much honey, so their populations are limited by the time of year w/ the least food available (pollen and nectar). The methods here help you figure out those bottlenecks if you want to target habitat restoration to boost pollinator populations. 2) Plants vary a lot in how much nectar and pollen they make. Not every crop makes flowers that feed pollinators (likely obvious, but some crops and cover crops are harvested or terminated before flowering, and wind-pollinated plants don't have nectar). Trees produce a ton of nectar and pollen. 3) The paper looked at two different ways to map land cover, and surprisingly the simpler approach worked as well (similar error levels)! It's a good reminder to always question whether you need more complexity and accuracy. If you just have a garden and want more bees and other pollinators, this blog post I wrote may help: https://sciencejon.blogspot.com/2024/05/new-paper-on-mapping-pollinator.html
 

WETLANDS:
The latest report on the status of wetlands in the US (excluding AK and HI) is a bummer but has some useful info. Key summaries are in Fig 9 and Table 2, but in short on net 221,000 acres of wetlands were converted, mostly to ag and tree plantations followed by housing developments. But that net change hides that fact that we actually lost 670,000 acres of vegetated wetlands, with non-vegetated wetlands like ponds, sandbars, and mudflats increasing (but NOT providing nearly as much ecological value). The report calls for more coordination to achieve no net loss of wetlands, to update and improve the National Wetlands Inventory, develop and implement better wetland conservation and management (duh), and commit to long-term monitoring and adaptive management.


REFERENCES:

Balch, J. K., Iglesias, V., Mahood, A. L., Cook, M. C., Amaral, C., DeCastro, A., Leyk, S., McIntosh, T. L., Nagy, R. C., St. Denis, L., Tuff, T., Verleye, E., Williams, A. P., & Kolden, C. A. (2024). The fastest-growing and most destructive fires in the US (2001 to 2020). Science, 386(6720), 425–431. https://doi.org/10.1126/science.adk5737
 
Brisco, E., Kulinskaya, E., & Koricheva, J. (2023). Assessment of temporal instability in the applied ecology and conservation evidence base. Research Synthesis Methods, November, 1–15. https://doi.org/10.1002/jrsm.1691
 
Flitcroft, R. L., Abell, R., Harrison, I., Arismendi, I., & Penaluna, B. E. (2023). Making global targets local for freshwater protection. Nature Sustainability. https://doi.org/10.1038/s41893-023-01193-7
 
George, M. M., Platts, S. V., Berry, B. A., Miller, M. F., Carlock, A. M., Horton, T. M., & George, M. H. (2024). Effect of SeaFeed, a canola oil infused with Asparagopsis armata , on methane emissions, animal health, performance, and carcass characteristics of Angus feedlot cattle. Translational Animal Science, 8(August). https://doi.org/10.1093/tas/txae116
 
Greenspoon, L., Krieger, E., Sender, R., Rosenberg, Y., Bar-On, Y. M., Moran, U., Antman, T., Meiri, S., Roll, U., Noor, E., & Milo, R. (2023). The global biomass of wild mammals. Proceedings of the National Academy of Sciences, 120(10), 2017. https://doi.org/10.1073/pnas.2204892120

REPLY AND COUNTER-REPLY TO GREENSPOON:

• Santini, L., Berzaghi, F., & Benítez-López, A. (2024). Total population reports are ill-suited for global biomass estimation of wild animals. Proceedings of the National Academy of Sciences, 121(4), 1–3. https://doi.org/10.1073/pnas.2308958121   
• Greenspoon, L., Rosenberg, Y., Meiri, S., Roll, U., Noor, E., & Milo, R. (2024). Reply to Santini et al.: Total population reports are necessary for global biomass estimation of wild mammals. Proceedings of the National Academy of Sciences of the United States of America, 121(4), 1–2. https://doi.org/10.1073/pnas.2316314121

Jasechko, S., Seybold, H., Perrone, D., Fan, Y., Shamsudduha, M., Taylor, R. G., Fallatah, O., & Kirchner, J. W. (2024). Rapid groundwater decline and some cases of recovery in aquifers globally. Nature, 625(7996), 715–721. https://doi.org/10.1038/s41586-023-06879-8
 
Lang, M. W., Ingebritsen, J. C., & Griffin, R. K. (2024). Status and Trends of Wetlands in the Conterminous United States 2009 to 2019. U.S. Department of the Interior; Fish and Wildlife Service, Washington, D.C. 43 pp. https://www.fws.gov/project/2019-wetlands-status-and-trends-report

Langhammer, P. F., Bull, J. W., Bicknell, J. E., Oakley, J. L., Brown, M. H., Bruford, M. W., Butchart, S. H. M., Carr, J. A., Church, D., Cooney, R., Cutajar, S., Foden, W., Foster, M. N., Gascon, C., Geldmann, J., Genovesi, P., Hoffmann, M., Howard-McCombe, J., Lewis, T., … Brooks, T. M. (2024). The positive impact of conservation action. Science, 384(6694), 453–458. https://doi.org/10.1126/science.adj6598

Li, K., Fisher, J., Power, A., & Iverson, A. (2024). A map of pollinator floral resource habitats in the agricultural landscape of Central New York. One Ecosystem, 9. https://doi.org/10.3897/oneeco.9.e118634
 
Littlefield, C. E., Suraci, J. P., Kintsch, J., Callahan, R., Cramer, P., Cross, M. S., Dickson, B. G., Duncan, L. A., Fisher, J. R., Freeman, P. T., Seidler, R., Wearn, A., Andrews, K. M., Brocki, M., Dodd, N., Gagnon, J., Johnson, A., Krosby, M., Skroch, M., & Sutherland, R. (2024). Evaluating and elevating the role of wildlife road crossings in climate adaptation. Frontiers in Ecology and the Environment, 1–10. https://doi.org/10.1002/fee.2816
 
Pivello, V. R., Vieira, I., Christianini, A. V., Ribeiro, D. B., da Silva Menezes, L., Berlinck, C. N., Melo, F. P. L., Marengo, J. A., Tornquist, C. G., Tomas, W. M., & Overbeck, G. E. (2021). Understanding Brazil’s catastrophic fires: Causes, consequences and policy needed to prevent future tragedies. Perspectives in Ecology and Conservation, 19(3), 233–255. https://doi.org/10.1016/j.pecon.2021.06.005
 
Sutherland, W. J., Bennett, C., Brotherton, P. N. M., Butchart, S. H. M., Butterworth, H. M., Clarke, S. J., Esmail, N., Fleishman, E., Gaston, K. J., Herbert-Read, J. E., Hughes, A. C., James, J., Kaartokallio, H., Le Roux, X., Lickorish, F. A., Newport, S., Palardy, J. E., Pearce-Higgins, J. W., Peck, L. S., … Thornton, A. (2024). A horizon scan of global biological conservation issues for 2024. Trends in Ecology & Evolution, 39(1), 89–100. https://doi.org/10.1016/j.tree.2023.11.001
 
Trencher, G., Nick, S., Carlson, J., & Johnson, M. (2024). Demand for low-quality offsets by major companies undermines climate integrity of the voluntary carbon market. Nature Communications, 15(1), 6863. https://doi.org/10.1038/s41467-024-51151-w
 
UNEP-WCMC, 2024. State of the World’s Migratory Species. UNEP-WCMC, Cambridge, United Kingdom.
https://www.cms.int/en/publication/state-worlds-migratory-species-report
 
Wang, H., Liu, J., Klaar, M., Chen, A., Gudmundsson, L., & Holden, J. (2024). Anthropogenic climate change has influenced global river flow seasonality. Science, 383(6686), 1009–1014. https://doi.org/10.1126/science.adi9501


Sincerely,
 
Jon
 
p.s. I inherited that Christmas sweater from my dad, and typically only pull it out once a year for a Christmas sing-along

June 2024 science summary

Greetings,

While I have heard that most of you want me to keep focusing on research articles (and I do have four this month, three on fire and one on pollinators), I also wanted to highlight two great books I've read.

First is "Eve: How the Female Body Drove 200 Million Years of Human Evolution" by Cat Bohannon. The intro has a really incisive indictment of how much biology research has centered on men, and how harmful that's been to both science and women in particular. It then delves into how and why various female traits evolved. I found it both fascinating and useful, and was shocked at how recent and limited efforts to better represent women in clinical trials have been. Here's a NYtimes review:
https://www.nytimes.com/2023/10/06/books/review/eve-cat-bohannon.html?unlocked_article_code=1.tU0.Ukhj.AMvoB5CNzRbt&smid=url-share

The other is About Us (https://goodreads.com/book/show/43726545-about-us), which is a collection of articles about many different forms of disability, each written by a person with lived experience (with one exception for people who are mostly unable to communicate, written by an ally). It seems like it would be a slog or a downer, but the articles are short, well-written, and really diverse in style which makes it a pretty quick and fun read (plus super educational). Some are funny, some made me cry (including some funny / sad mixes), but all were worth reading. If you are a New York Times subscriber all the component articles are free, but I liked having it in book form. If you're in DC and want to borrow a copy let me know!

If you know someone who wants to sign up to receive these summaries, they can do so at http://bit.ly/sciencejon (no need to email me).

POLLINATORS:
Li et al. 2024 is a methods paper about using land cover data to predict floral resource availability for pollinators. I'm an author despite minimal input; the lead author based this on work by the last author, who I provided some guidance to when he was a postdoc. There are a few potentially interesting things in here. 1) Most pollinators don't make much honey, so their populations are limited by the time of year w/ the least food available (pollen and nectar). The methods here help you figure out those bottlenecks if you want to target habitat restoration to boost pollinator populations. 2) Plants vary a lot in how much nectar pollen they make. Not every crop makes flowers that feed pollinators (likely obvious, but some crops and cover crops are harvested or terminated before flowering, and wind-pollinated plants don't have nectar). Trees produce a ton of nectar and pollen. 3) The paper looked at two different ways to map land cover, and surprisingly the simpler approach worked as well (similar error levels)! It's a good reminder to always question whether you need more complexity and accuracy.

I added some tips for improving pollinator habitat in your own garden here.


FIRE:
Parks et al. 2023 looks at severity and frequency of fire in dry conifer forests in the Western US (see Fig 1), comparing the last 40 years to pre-colonial times. They found that forests that kill most or all trees ("stand-replacing fires") are from 3 to 14 times more common now (varying by ecoregion). By looking at areas with varying logging pressures and fire suppression, they show that logging is not reducing stand-replacing fires, but places w/ more prescribed fire and the least fire suppression have much less of these severe fires. For example, in the Gila Wilderness (where many fires are not suppressed) the % of fires that were stand-replacing was 3 times lower than the ecoregion it's in. Prescribed fires consistently led to the lowest stand-replacement, at similar rates to pre-colonial times. Fig 4 and 5 have some great aerial images of forests before and after fire and changes over decades.

Peeler et al. 2023 is an analysis of the best places in 11 US Western states for coniferous forest management (removing small trees and brush, and/or prescribed fire) to reduce the risk of wildfire leading to carbon loss (and/or to protect human communities). Skip to Fig 5 for the key results (the highest ranked places they found) and Fig 3 for more detail. Note that they excluded forests which historically burned rarely b/c ecologically these kinds of forests are supposed to be dense and thinning would alter that ecology (but they still see a role for prescribed fire and tree planting there). They also flag the need for cross-boundary collaboration (including w/ local & Indigenous knowledge and values).

Vidal-Riveros et al. 2023 looks at wildfire history and impacts across the Gran Chaco region (see Fig 1 - it's mostly in Argentina and Paraguay with some in Bolivia and a tiny bit in Brazil, and includes two ecoregions). It's a good review, but they note that the literature has some big gaps. It is mostly focused in Argentina (69% of papers they assessed) with only 10% in Bolivia and 3% in Paraguay. 68% of the papers were on remote sensing of fire frequency, most of which lacked field calibration and validation (which is really important). Unsurprisingly cattle ranching is the main source of wildfire, and in many cases is frequent enough to make it hard for vegetation to recover. For example, in Bolivia 4 yr burning cycles don't allow for forest and soil regeneration, while leaving land fallow for 14-20 years after fire (in Argentina) promotes plant diversity and weed control. The paper has some good info on how different plant species and communities respond to fire. It notes there's limited info on how fire affects invasive non-native plants, but one study in Argentina found prescribed fire killed native and non-native species at similar levels (and some highly flammable non-native spp promote flame spreading). Fig 3 has a nice model of how fire and grazing interact to shape whether grass or trees or shrubs dominate in a given place.


REFERENCES:
Li, K., Fisher, J., Power, A., & Iverson, A. (2024). A map of pollinator floral resource habitats in the agricultural landscape of Central New York. One Ecosystem, 9. https://doi.org/10.3897/oneeco.9.e118634

Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544(June), 121232. https://doi.org/10.1016/j.foreco.2023.121232

Peeler, J. L., McCauley, L., Metlen, K. L., Woolley, T., Davis, K. T., Robles, M. D., Haugo, R. D., Riley, K. L., Higuera, P. E., Fargione, J. E., Addington, R. N., Bassett, S., Blankenship, K., Case, M. J., Chapman, T. B., Smith, E., Swaty, R., & Welch, N. (2023). Identifying opportunity hot spots for reducing the risk of wildfire-caused carbon loss in western US conifer forests. Environmental Research Letters, 18(9), 094040. https://doi.org/10.1088/1748-9326/acf05a

Vidal-Riveros, C., Souza-Alonso, P., Bravo, S., Laino, R., & Ngo Bieng, M. A. (2023). A review of wildfires effects across the Gran Chaco region. Forest Ecology and Management, 549(September), 121432. https://doi.org/10.1016/j.foreco.2023.121432

Sincerely,
 
Jon
 
p.s. This is a photo of a long-horned bee (Melissodes spp.) which I only ever saw in my garden the one year I grew a couple sunflowers. They look even cooler close up: photo 1, photo 2, photo 3

Pollinators - new paper and tips for your garden

I wanted to announce a new paper I've been kindly included as an author on (despite minimal contributions) - Li et al. 2024. It's a methods paper about using land cover data to predict floral resource availability for pollinators. There are a few potentially interesting things in here. 1) Most pollinators don't make much honey, so their populations are limited by the time of year w/ the least food available (pollen and nectar). The methods here help you figure out those bottlenecks if you want to target habitat restoration to boost pollinator populations. 2) Plants vary a lot in how much nectar pollen they make. Not every crop makes flowers that feed pollinators (likely obvious, but some crops and cover crops are harvested or terminated before flowering, and wind-pollinated plants don't have nectar). Trees produce a ton of nectar and pollen. 3) The paper looked at two different ways to map land cover, and surprisingly the simpler approach worked as well (similar error levels)! It's a good reminder to always question whether you need more complexity and accuracy. https://oneecosystem.pensoft.net/article/118634/

I was asked "How can we use these insights in NYC if at all for urban pollinator husbandry?" which made me realize I should have been more clear about tips for people who want their gardens to better support pollinators.

The actual results are specific to upstate New York and wouldn't apply elsewhere. To make this work one of the authors had to visit many places to see what plants were blooming in what kinds of habitat at different times, then use remote sensing to make a land cover map, then do the math to see when floral resources are scarce.BUT here's how I have been using the very rough concept it in my own garden!

1. Take notes and photos throughout the year as you walk around your neighborhood. When do you first see bees (and/or other pollinators like flies and beetles), and what flowers are they visiting? If you're not seeing bees in your garden - try planting those early bloomers in your own yard.

2. What weeks do you notice the most and least flowers? This isn't a perfect proxy since some flowers have big petals but don't provide much food (like marigolds, geraniums, lilies, and tulips). But it's a start. Write down the weeks where you see the fewest flowers in the neighborhood. That tells you where your garden can have the most added value.

3. Are there certain plants absolutely mobbed with pollinators certain weeks (bees, flies, moths, etc.)? That's a good clue they may be offering food when it's scarce, and/or it's high quality, and you could plant more of them. If you want diverse pollinators, include some plants with small composite flowers (I find those are the most popular overall, especially for sweat bees and bomber flies, something like anise hyssop / Agastache or goldenrod) and some with bigger flowers larger bees like (Penstemon is a favorite of my bees, although the bees also love basil flowers).

4. Based on your notes, add perennial plants that flower when there are the fewest available flowers in the neighborhood. For me that was early spring, late fall, and mid to late summer. Consider also adding some plants that flower intermittently year round like rosemary - it's consistently a star performer in late winter / early spring for me, but also gets some love in the summer. For folks in the DC area my top performers are probably penstemon, anise hyssop, goldenrod, swamp milkweed, and obedient plant (for late fall / early winter)

5. Take notes and/or photos of what you see in your garden. It's fun to see how specific flowers will attract species that won't come otherwise. Use Google Lens or iNaturalist to identify at least the rough kinds of bees. Look for the metallic green or orange Agopostemon bees, get close photos of sweat bees, and whatever other ones surprise you. Here are my pics of pollinators in my garden.

6. Experiment! One year I planted sunflower and it was the only time I saw a long-horned bee in my garden (check out the pics: it's a pretty cool bee). I used to have some lambs ear which I got rid of b/c it wasn't native, but then I stopped seeing carder bees (which collected its fuzz).

7. Leave the dead flower stems through the winter; when new shoots and leaves form on the plant, break off the stems at different heights and toss them elsewhere in your garden (not compost). Many bees and other pollinators lay their eggs in the stems and you don't want to get rid of them before they hatch. See this guide from Xerces for more.

8. Have fun. It's really cool to see how much impact you can have on your garden and neighborhood.

9. Don't forget about habitat for other wildlife! My favorites: 

a) add a birdbath if you're able to commit to dumping and replacing the water daily (you can use rain barrel water like I do). Scrub it with a brush weekly. Get one w/ rough iron sides or leave in a stick so bugs can drink but escape if they fall in.

b) make sure you have some bushes for birds to hang out in. Mine love the swamp dogwood and viburnum more than the inkberries I planted specifically for birds.

c) if you're in the Mid-Atlantic, plant cut-leaf coneflowers. You get 7-8' tall plants that attract so many goldfinches that eat the seeds!

d) let some of your herbs flower. In addition to bees loving basil, cardinals love coriander seeds from cilantro!

e) pokeweed is a native aggressive perennial that provides so much free bird food, especially to catbirds but also robins and mockingbirds and sometimes other species. Cut it back or dig it up when it spreads too much.

e) if you have room, make a brush pile from any pokeweed stems and woody stems and bush trimmings. Several species appreciate them.

f) I used to think "certified wildlife friendly" signs were silly and bragging, but then I heard some neighbors walk by complaining about how unruly my garden was (they didn't see me on the porch). I ordered a sign, and a week or so after I put it up, I heard the same neighbors walk by, see the sign, and say "oh that's cool! it's a wildlife-friendly garden!" So it's worth looking into and the process has a few more tips.

June 2018 science journal article roundup

Hi,

My garden is abuzz with bees and flies (the photo above is of a bee the size of a gnat), which has me thinking about pollinators and pesticides - the focus of this roundup. But I couldn't resist including one study on improving watershed-scale water quality via changing agriculture, as I've been gushing about it for years (hat tip to Steve Richter from TNC Wisconsin). Enjoy!

If you want to receive these monthly summaries by email you can sign up at http://eepurl.com/diB0nr, and if you want an email anytime I post something on this blog you can subscribe using the form on the top right of this page.

AGRICULTURE & WATER QUALITY:
Carvin et al 2018 is a study I've been eagerly awaiting for years. It is a rigorous paired watershed study looking at the impact of a carefully targeted set of agricultural interventions, and is one of the first papers in the US to show we CAN improve water quality at a watershed scale (50 km2) through shifting ag. Initial work had found 9% of the area was contributing 40% of the phosphorous load, so the authors really targeted those heavy contributors. They found a 55% reduction in phosphorus runoff loads and suspended sediment event loads decreased by 52% for events during unfrozen soil conditions  into the Pecatonica River tributary during storm events. This is big news as these outcomes have been elusive. However, this watershed was picked as one of the most likely to respond well, and those seeking to replicate these results should also carefully select their watersheds. Contact Steve Richter at TNC for more info.


POLLINATORS:
Klein et al. 2007 is a fantastic reference examining dependence on animal pollination across 115 major crop species (ignoring crops like corn which are entirely wind-pollinated). I mainly use Appendix 2, which for each crop lists how much it benefits from animal pollination (from entirely dependent on animal pollinators like cocoa or squash, to receiving almost no benefit) as well as listing the type of pollinator, pointing to references, etc. While the appendix is my favorite part, they also note in the main paper that a) non-insect pollinators (e.g. birds and bats) are less well studied and b) as agriculture intensifies wild pollinators are likely to decline. This means thinking about pollinator habitat in and around farms can be important for some crops, and the appendix can identify which ones are most likely to see more benefit.

Garibaldi et al 2016 argue that improving pollination is an underappreciated need to close crop yield gaps. They found that yields on small farms (<2 ha) could be improved by 24% on average by boosting pollinator density. Strangely for larger farms, when polinator diversity was low, yields actually dropped with incresing pollinator density (when diversity was high, yields went up with pollinator density as expected). The authors don't explain why (or even accurately convey that finding in the text), which makes me wonder if the sample was too small. They did find that isolation from natural habitats was one of the most important predictors of crop yield. This calls attention to the need for more specific data on how restoring habitat could boost crop yields (including testing crops and regions likely to receive the most benefit).

I recently wondered if camera traps and audio monitoring would work for pollinators, and Edwards et al. 2015 had a crafty idea that worked well: long-term time lapse video. They looked at visits by pollinators to 30 different plant species, then focus on a species of dogwood and had nearly complete records for a given flower. Check out Figure 1 and 2, you can clearly not only see the rough type of pollinator, but even see pollination take place as florets within the inflorescence close (a cluster of flowers, for a dogwood this looks like 1 "flower"). The system is relatively cheap and simple, and perhaps the biggest obstacle to doing lots of this is the need to manually review each video to classify pollinators seen in each frame (an hour of footage plays in 1.75 minutes, but scoring takes longer). There's also a question of how many flowers of how many species you'd need to monitoring to get a sense of total pollinator activity on a given piece of land. Still a really cool setup worth keeping an eye on.

I was recently surprised to hear that soybean can benefit from insect pollination (despite self-pollinating). Milfont et al. 2013 demonstrates this under field conditions (including typical pesticide application) in Brazil. They found wild pollinators may boost soy yields by 6%, and adding honeybees on top of wild pollinators raised yields 18%. They either caged plants to prevent access by pollinators, left them open (and did sampling for pollinators), or added honeybees nearby (without caging the bees to force pollination). The exciting thing is if even intense industrial soy gets a 6% boost, there is potential for soy with more careful pesticide application and more integrated pollinator habitat to do considerably better.

Gill and O'Neal 2015 also looks at insect pollination of soy, but focusing on the pollinators in Iowa rather than crop yield. They did lots of sampling, collecting >5,000 individuals from >50 species. 29-38% of the bees they sampled had collected at least some soy pollen. Strangely, although honeybee colonies were present on or near the farms they studied, they found almost no honeybees in their traps. This again emphasizes the potential value of wild pollinators. As an aside: the most common species of pollinator they found is one of the coolest kinds of bees I've ever seen (Agapostemon virescens, see the photo at the end of this email).


PESTICIDES / PEST CONTROL:
Eng et al 2017 provides the first experimental evidence that ingesting neonicotinoids (imidacloprid) and organophosphates (chlorpyrifos) can directly harm songbirds. Birds were fed low doses (the amount typically found on <0.1 corn seed, ~4 canola seeds) or high doses (0.2 corn seed, or 9 canola seeds) and lost 17-25% of their weight within 3 days of being dosed (for imidacloprid only) and were unable to sense north (which could impair migration), although they recovered within 14 days. This is concerning as birds may eat spilled treated seed (or even granules of the pesticide directly), which could lead to reduced breeding success. On the other hand, for some seeds birds typically remove seed hulls before eating the seed, which would reduce the effective dose. You can read a newspaper article about it here: https://amp.theguardian.com/environment/2017/nov/29/common-pesticide-can-make-migrating-birds-lose-their-way-research-shows and read the paper here: https://www.nature.com/articles/s41598-017-15446-x.epdf?author_access_token=60vOAq7fy3uoItENRL_WLtRgN0jAjWel9jnR3ZoTv0PBos7CYdu4-aOFIzRGcQZYPhLZT79bnumB3G0JwKQDqd8sXxokuXX20RybZGim1WNULIibibaVSnXR6616CbBcOjFXccxNhEZR_Q54lKeJqg%3D%3D

Tooker et al 2017 tackles a hot topic - what role do neonicotinoid seed treatments (NST) have in integrated pest management? Many ag companies assert they fit in well, since they can reduce aerial sprays which would have higher impact. On the other hand, there are concerns about effects on nontarget species, potential for resistance, and universal prophylactic application as opposed to the usual IPM approach of deploying pesticides in response to a pest outbreak. They have some interesting findings. First, they find that NST mostly target relatively uncommon pests by using almost universal application more suited to severe pests. They also note that current use of NST on corn and soy is much higher than historic benchmarks, indicating NST is not simply displacing other pesticides. They conclude by noting that more careful use of neonics is likely to both retain their value for pest control longer (by slowing down resistance), and that the challenge in finding corn and soy seeds without NST should be addressed.

Lechenet et al. 2017 looks at almost 1,000 farms in France, comparing farms with similar context to look at how the frequency of pesticide application relates to yield. They estimated that 3/4 of farms could reduce pesticide use without reducing yield or profit, and that on average for farms where they could get more specific, pesticide could be reduced on average by 42%. It's important to note they looked at correlations and predictions rather than empirically testing interventions, and they note that these reductions would likely be challenging for farmers.  Nonetheless, the article shows the importance of evaluating pest control strategies and looking for ways to reduce pesticide use.

I don't totally buy all of the conclusions of Bøhn and Lövei 2017, but they present some pretty interesting case studies. The basic theme is that a simple reductionist approach to pest control via GM-traits is unlikely to solve complex pest problems. They come out arguing that pesticides and transgenic traits are unlikely to be successful but also don't present clear alternatives. To me the interesting part of the paper is looking at the set of responses to a new transgenic plant (especially the surprises), and using that to think about what was missing and how we could build more robust pest control systems with more forethought and better design.

Bueno et al. 2017 is a primer on integrated pest management (IPM) for soybeans in Brazil. They list key pests, provide recommendations for scouting / sampling methods, evaluate several control methods (viruses, natural predators / parasitoids, insecticides, etc.). They also address how different pesticides impact natural enemies, finding that thiamethoxam harms natural enemies enough to actually allow pests to increase (although this is based on unpublished data, and appearing in a fairly low-quality journal, so it's an interesting thing to look into rather than a solid result). I see this article as a useful set of issues to consider for people working in this space.


REFERENCES:
Bøhn, T., & Lövei, G. L. (2017). Complex Outcomes from Insect and Weed Control with Transgenic Plants: Ecological Surprises? Frontiers in Environmental Science, 5(September), 1–8. https://doi.org/10.3389/fenvs.2017.00060

Bueno, R. C. O. F., Raetano, C. G., Junior, J. D., & Carvalho, F. K. (2017). Integrated Management of Soybean Pests: The Example of Brazil. Outlooks on Pest Management, (August), 149–153. https://doi.org/10.1564/v28

Carvin, R., Good, L. W., Fitzpatrick, F., Diehl, C., Songer, K., Meyer, K. J., … Richter, S. (2018). Testing a two-scale focused conservation strategy for reducing phosphorus and sediment loads from agricultural watersheds. Journal of Soil and Water Conservation, 73(3), 298–309. https://doi.org/10.2489/jswc.73.3.298

Edwards, J., Smith, G. P., & Mcentee, M. H. F. (2015). Long-term time-lapse video provides near complete records of floral visitation. Journal of Pollination Ecology, 16(13), 91–100.

Eng, M. L., Stutchbury, B. J. M., & Morrissey, C. A. (2017). Imidacloprid and chlorpyrifos insecticides impair migratory ability in a seed-eating songbird. Scientific Reports, 7(1), 1–9. https://doi.org/10.1038/s41598-017-15446-x

Garibaldi, L. A., Carvalheiro, L. G., Vaissière, B. E., Gemmill-herren, B., Hipólito, J., Freitas, B. M., … Zhang, H. (2016). Mutually beneficial pollinator diversity and crop yield outcomes in small and large farms. Science, 351(6271), 388–391. https://doi.org/10.1126/science.aac7287

Gill, K. A., & O’Neal, M. E. (2015). Survey of soybean insect pollinators: Community identification and sampling method analysis. Environmental Entomology, 44(3), 488–498. https://doi.org/10.1093/ee/nvv001

Klein, A.-M., Vaissière, B. E., Cane, J. H., Steffan-Dewenter, I., Cunningham, S. a, Kremen, C., & Tscharntke, T. (2007). Importance of pollinators in changing landscapes for world crops. Proceedings. Biological Sciences / The Royal Society, 274(1608), 303–313. https://doi.org/10.1098/rspb.2006.3721

Lechenet, M., Dessaint, F., Py, G., Makowski, D., & Munier-Jolain, N. (2017). Reducing pesticide use while preserving crop productivity and profitability on arable farms. Nature Plants, 3(3), 17008. https://doi.org/10.1038/nplants.2017.8

de O. Milfont, M., Rocha, E. E. M., Lima, A. O. N., & Freitas, B. M. (2013). Higher soybean production using honeybee and wild pollinators, a sustainable alternative to pesticides and autopollination. Environmental Chemistry Letters, 11(4), 335–341. https://doi.org/10.1007/s10311-013-0412-8

Tooker, J. F., Douglas, M. R., & Krupke, C. H. (2017). Neonicotinoid Seed Treatments: Limitations and Compatibility with Integrated Pest Management. Agricultural & Environmental Letters, 2(1), 0. https://doi.org/10.2134/ael2017.08.0026

Sincerely,

Jon

p.s. as a reminder, you can search all of the science articles written by TNC staff (that we know of) here http://www.conservationgateway.org/ConservationPlanning/ToolsData/sitepages/article-list.aspx
(as you publish please email science_pubs@tnc.org to help keep this resource current).
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 http://sciencejon.blogspot.com/

Bonus photo: here's the type of bee Gill and O'Neal 2015 saw the most on soy fields in Iowa (Agapostemon, this one is on a dahlia in my garden):