Evan Fricke
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efricke.bsky.social
Evan Fricke
@efricke.bsky.social
350 followers 530 following 20 posts
Biodiversity, ecology, climate change, forests, seed dispersers.
Research scientist at MIT.
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efricke.bsky.social
Very cool to see our recent study turned into a cartoon (what!?)

Anyone else want to skip the middleman and just publish cartoons from here on out?

🔗 www.pnas.org/doi/abs/10.1...
This cartoon panel shows a tropical forest with tapir, monkey, thrush, and tortoise. The text reads: In tropical forests, animals play an important role in reforestation - often by eating seeds and then dispersing them through their, uh... poop! This panel shows cartoon drawings of a Sumatran rhino, bare-throated bellbird, Mariana flying fox, and mountain gorilla. The text reads: But as wildlife populations decline due to habitat loss, invasive species and poaching, seed dispersal also slows. The panel has a sparse forested landscape with just the thrush remaining. The text reads: "A new study found that, due to animal losses, the potential for carbon storage from natural forest regrowth has been cut in half. The last panel shows a tapir dispersing seeds. The text reads: Reforestation can be one of the most effective natural climate solutions. To unlock its full potential, we must restore and protect nature's seed dispersers. The credit text says: Mikhalia Markham / The Nature Conservancy.
August 26, 2025 at 8:01 PM
efricke.bsky.social
MIT homepage today:
40% hornbill
40% figs
20% me yelling about seed dispersers

Press release here: mit.edu
Screenshot of the MIT homepage with a story about our recent PNAS article. The text reads: A new study shows fruit-eating animals help tropical forests absorb carbon, by dispersing seeds and enabling new trees to grow. “When we lose our animals, we’re losing the ecological infrastructure that keeps our tropical forests healthy and resilient,” Evan Fricke says.
July 30, 2025 at 3:08 PM
efricke.bsky.social
The take-home message is clear.

Overlooking nature’s tree planters risks missing ‘win-win’ pathways for both climate mitigation and biodiversity conservation.
A young bonobo (Pan paniscus) eats a Mammea africana fruit in a Congolese forest, dispersing the large seeds of this tropical tree. The ecological role of this endangered seed disperser is threatened by habitat loss, fragmentation, and illegal hunting within their restricted range. Image credit: Christian Ziegler.
July 28, 2025 at 4:41 PM
efricke.bsky.social
These numbers help show where natural regrowth can be effective, in which areas a human hand is needed to meet climate mitigation potential, or how we can leverage seed dispersers’ roles to amplify forest restoration.
Figure showing the mapping of aboveground carbon accumulation potential in light of seed dispersal disruption. (A) The current (c. 2020) regrowth potential of tropical forest and savanna ecosystems while accounting for seed dispersal disruption. Hatching indicates savanna biomes. Estimates of model uncertainty are presented in Fig. S7. (B) The cumulative effect of land use change over the period 2000-2020 on natural regrowth potential. (C) the impact of seed dispersal disruption on regrowth potential in tropical forest areas. Values estimate the degree to which current levels of seed dispersal disruption would limit carbon accumulation for regrowing forests at each location. Inset panel shows the distribution of lost carbon accumulation potential across sites identified as potential restoration areas by ref. (36) that occur in the tropical forest biomes. Model uncertainty is presented in Fig. S8.
July 28, 2025 at 4:41 PM
efricke.bsky.social
Despite seed disperser decline, natural regrowth still matches or exceeds the carbon gains of tree planting by people in many areas.

And natural regrowth often has much lower implementation costs and better biodiversity outcomes.
Figure showing effect of seed dispersal disruption on aboveground carbon accumulation. (A) Stand age versus fitted values of aboveground carbon during natural regrowth, with color gradient showing levels of seed dispersal disruption at each site. (B) Standardized effect sizes representing the effect of a 1 SD increase in the predictor variable on carbon accumulation rates annualized over the first 30 years of regrowth. Bars show 95% and 99% CIs, points show median posterior values, and filled points indicate 95% CIs that do not overlap zero. (C) Annualized carbon accumulation rate under either natural regrowth or monoculture plantation without other reported interventions such as fertilization and irrigation, with lines showing model estimates for average environmental conditions and shaded areas showing 95% credible intervals.
July 28, 2025 at 4:41 PM
efricke.bsky.social
Two key findings:

-Aboveground carbon accumulates 4x faster in regrowing tropical forests where seed dispersal by animals is most intact vs. most disrupted.

-Current seed dispersal disruption levels cut carbon uptake of proposed reforestation sites by 57% on average.
A great hornbill (Buceros bicornis) eats a fig in Royal Manas National Park, Bhutan. Hornbills are key long-distance seed dispersers in Asian tropical forests, but forest degradation, hunting, and wildlife trade threaten the ecological roles they play. Image credit: Christian Ziegler.
July 28, 2025 at 4:41 PM
efricke.bsky.social
We combined results of thousands of local field studies on seed-dispersing animals and human impacts to map a ‘seed dispersal disruption’ index across the tropics.

We then paired it with carbon accumulation data from thousands of tropical regrowth plots, along with other environmental variables.
Figure showing the modeling seed dispersal disruption. (A) Example of the processes modeled to estimate seed dispersal function, showing observed seed retention times versus model-predicted values based on species traits by ref. (28) (see also Fig. S2). (B) Observed relationship between the human footprint index and displacement distances over a typical seed retention period, based on field observations of animal movement; detailed results are presented in Figure S3. (C-H), examples of seed dispersal disruption values and distribution of values across regional scales; dashed lines show estimates c. 2000 and filled area shows estimates c. 2020. Inset plots show areas in the Amazon Basin (C), the Congo Basin (E), and Borneo (G).
July 28, 2025 at 4:41 PM
efricke.bsky.social
For #BiodiversityDay, check out some of the mammals that “should” be in Southern California today (species that went extinct since the last interglacial are greyed out).

From our paper www.science.org/doi/10.1126/... Illustrated by coauthor @ohsanisidro.bsky.social
An illustration of mammal species that would naturally occur near La Brea, California, with color used to show species that still exist there like coyotes and mule deer, and greyscale used to show extinct species like ground sloths and saber-toothed cats. Illustration credit: Oscar Sanisidro.
May 22, 2025 at 5:07 PM
efricke.bsky.social
We’d love your help spreading this (the message, not the seeds - though both matter!)

Big thanks to the stellar coauthors: Carolina Bello, Becky Chaplin-Kramer (@beckyck.bsky.social), Daisy Dent, Ken Feeley (@kjfeeley.bsky.social), Mauro Galetti, Juanpe González-Varo, Ruben Heleno, Leighton Reid.
Photo of seed dispersal by Vireo gracilirostris, an important seed disperser on the oceanic island of Fernando de Noronha in Brazil where this species is endemic.
May 19, 2025 at 1:35 AM
efricke.bsky.social
But we’re making progress.

New data syntheses and models are capturing functional changes across large scales, helping reveal long-term impacts, which range from reduced forest product provisioning and weakened carbon storage to impaired wildfire recovery and degraded habitats for animals.
Example results from a study modeling seed dispersal function. The figure has two panels with scatter plots with points representing ecoregion globally. The y axis in each is change in long-distance seed dispersal function and the x axis is change in animal species richness and functional diversity, respectively. These results show that losses of bird and mammal species or functional diversity correspond to far greater proportional losses of seed dispersal function. https://www.science.org/doi/epdf/10.1126/science.abk3510
May 19, 2025 at 1:35 AM
efricke.bsky.social
Why are seed dispersers missing from the conversation?

One idea: Experiments can demonstrate societally relevant impacts of pollinator decline within a growing season. For seed disperser decline, they unfold slowly, across vast scales, and experiments at scale are unfeasible or unethical.
Screenshot of a Google Trends query showing search interest from 2004 to today, comparing the search terms “seed disperser” and “pollinator”. The pollinator line is increasing over time while the seed disperser line is stuck at zero interest.
May 19, 2025 at 1:35 AM
efricke.bsky.social
Seed disperser decline threatens plant biodiversity, connectivity, and resilience.

Yet despite these being core goals of global efforts to protect, manage, and restore nature, the roles of seed dispersers remain largely overlooked in global biodiversity and restoration strategies.
Figure from the review article showing that seed disperser decline can reduce plant biodiversity, ecosystem function, and long-term resilience of ecosystems. Relative to the baseline of high-integrity landscapes with robust seed disperser assemblages (shown at left), ecosystems within fragmented and degraded habitats (in the middle middle) have lower seed dispersal function, especially through losses of large-bodied seed dispersers; these losses reduce several aspects of ecosystem function. Habitats that are potentially suitable under future climates (at the right) for the plants at the left receive fewer seeds through dispersal, reducing gene flow and threatening the capacity of ecosystems to adapt to climate change.
May 19, 2025 at 1:35 AM
efricke.bsky.social
The majority of plant species rely on animals to move their seeds. Birds, mammals, and other seed dispersers shape plant biodiversity, recovery from disturbance, and responses to climate change.

But this is breaking down as seed disperser diversity, abundance, and movement decline worldwide.
Figure from the review article with several panels. The first shows declines in seed disperser species richness, body mass, movement, range size, and population size spanning ~6% to ~30% for each. The next shows that seed disperser species have higher proportions of threatened and endangered species than other groups of animals. The last three panels show maps of mammalian seed disperser losses due to extinction, losses and gains of range size, and potential losses of endangered animals. For each of these three maps, most regions have substantially lost seed dispersers, have seed dispersers that exist in smaller ranges, or have many endangered seed dispersers.
May 19, 2025 at 1:35 AM