In the Mexican state of Veracruz, on an old cattle pasture in Los Tuxtlas, over seventeen years the number of plants was nearly twice the control level. The reason turned out to lie not in the volume of plantings but in the choice of species: where trees were planted whose fruits are relished by birds and bats, nature came back to life noticeably faster.
The experiment began in June 2006 on twelve hectares of actively grazed pasture adjoining secondary forest within the biosphere reserve. Luis Carlos Beltrán, lead author of the work from the Pontifical Xavierian University in Bogotá, and his colleagues divided the site into twenty-four plots measuring 30 by 30 meters, separated from one another by strips of pasture. Eight plots were planted with twelve tree species whose seeds are dispersed by animals. Another eight were planted with species whose seeds are carried by the wind, and eight were left to regenerate on their own. Each planted plot received 144 seedlings, so that the number of plantings was compared fairly.
This place was once home to humid lowland tropical forest. Around the 1960s it was cleared by fire to grow a single crop of maize for one sowing season, and then the land was taken over by grass for cattle. That is precisely why recovery is slow: the seed bank vanished along with the forest, and it has to be brought back piece by piece.
In July 2023, seventeen years after the start, the researchers walked all twenty-four plots and recorded every woody plant and palm from 40 centimeters to 2,25 meter in height that had appeared there without human involvement. In total 4847 plants from 109 taxa were counted. On the plots with animal-dispersed trees there grew on average 253 plants, while on the naturally regenerating plots there were 134. Species diversity was higher too: on average 33,5 species on the animal-dispersed plots.
Why does this work? Fruiting trees lure birds and bats, which bring seeds from neighboring forests. In an earlier study at the same site, fruit-eating bats turned out to be more numerous precisely on the plots with animal-dispersed plantings. Birds dispersed the seeds of late-successional trees, and on the planted plots their numbers rose noticeably. Curiously, bird diversity and abundance were higher precisely on the naturally regenerating plots, meaning that plantings do not shape the composition of newcomers in the same way everywhere.
The wind-dispersed plots produced an intermediate result. Nearly a quarter (23,8%) of the recruitment on them came from a single species, Vochysia guatemalensis. This tree begins to bear fruit just four years after planting, which is usually characteristic of pioneers. But when the researchers excluded the offspring of the planted trees themselves, the advantage of the animal-dispersed plots held: on average 241 new plant versus 164 on the wind-dispersed ones. After thirteen years the picture for the wind-dispersed plantings turned out different: there were more trees taller than two meters. So a fast start and a long-term outcome can diverge.
After twelve years the canopy on the animal-dispersed plots had closed to 88%, on the wind-dispersed ones to 83%, and on the naturally regenerating plots only to 62%. The gap is especially important in the context of broader observations: long-term studies show that tree plantings increase the abundance of late species compared with natural regeneration.
The study, published in September 2026 in the journal Forest Ecology and Management, shows the main point: the volume of plantings by itself decides nothing. What matters is which links between plants and animals are set in motion. Birds and bats continue the work that people only began, and which trees are planted determines who will disperse the seeds onward.
The results matter not only for Mexico. They show that restoring degraded land proceeds faster when people take account of the connections that already exist in nature rather than trying to replace them with a scheme of their own. Los Tuxtlas is still far from mature forest, but the choice of species already today determines what it will be like and who will colonize it.
