Peccaries are doing soil chemistry, and intact canopy no longer proves a forest works

The chemistry pivots on aluminium. It damages plants at high concentrations, and the study reports less of it where animal presence was greater ^[8]. Leticia Goncalves Ribeiro, the lead author, describes aluminium, pH and calcium as linked, with fertility depending on the balance between them rather than on any single reading ^[8]. Above the soil the pathway is mechanical. Rooting and trampling break litter into smaller pieces and spread it more evenly, which increases contact with the soil and speeds the breakdown of lignin, the molecule that coats plant cells and slows decay ^[9]. Litter in the accessible plots also held a more even mix of leaves, twigs, fruits and seeds, which helps it rot ^[10]. Nothing here is fertiliser arriving from outside. The animals are accelerating the release of what the forest already dropped, and Ribeiro attributes the disturbance mainly to peccaries working the ground for fallen fruit and seeds while defecating and urinating across it ^[5].

The measurement side deserves plain description. Plots are 15 square meters each ^[12], so the twenty used in this analysis ^[1] amount to roughly 300 square meters of forest floor ^[2]. What carries the inference is not area but time: the exclosures have stood in the Serra do Mar range since 2009 ^[12], long enough for the contrast to be an accumulation rather than a snapshot. The exposure variable, mammal biomass, is estimated from camera trap images ^[14], which is the softer half of an otherwise hard design. And the account gives direction without magnitude, with no effect sizes attached to the pH, calcium, aluminium or lignin differences ^[3].

The project behind the data, DEFAU-BIOTA, is framed around the effects of defaunation on soil carbon and functional plant diversity ^[12]. What has been announced stops at soil chemistry and litter composition ^[1]. That gap is the commercially relevant one, because carbon is the unit anyone pays for and pH is not.

The awkward part is what this does to verification. Carlos Botelho State Park sits inside a large mosaic of protected Atlantic Forest in the Vale do Ribeira ^[13], the sort of place that scores well on any canopy measure. Mauro Galetti, who coordinated the study, calls the hunted herbivores ecosystem engineers whose influence reaches plant composition and soil chemistry alike ^[11]. If that holds, a park can keep its trees in the imagery and still lose the process holding its topsoil out of the acid range, and the imagery will not report it ^[2]. The work was done by CBioClima at the Institute of Biosciences of Sao Paulo State University in Rio Claro ^[15], on a biome where the relevant animals are already in decline ^[3].