2.2 Forest states
To define the gradient of ecosystem degradation in the region, we used
the state-transition model developed by Jara-Guerrero et al. (2019).
Based on expert scientific and local knowledge, this model identifies
five states of the SDTF of Ecuador, which can be differentiated
according to vegetation structure, species diversity, and the drivers
leading to each state. These states are:
- Natural forest : High richness of woody plants and high canopy
cover with three clear strata (arboreal, shrub and herbaceous) and
abundant natural regeneration. Resource extraction is low and limited
to small areas.
- Semi-natural forest : Lower woody species richness, tree
density and natural regeneration compared to natural forest, as well
as higher density of herbaceous and shrub species. Persistent
livestock grazing (primarily by goats) and/or selective logging drive
the transition from natural to semi-natural forest over time.
- Shrub-dominated forest : Significantly reduced woody species
richness, tree density and regeneration. Trees are isolated or absent
and the shrub and herbaceous strata dominate. Common species tend to
have high wood density that likely enables them to resist browsing by
livestock. Intensification of grazing pressure and logging trigger the
transition from semi-natural forest to this state over time.
- Simplified forest: Dominance of the tree layer by one or a
few species (e.g., Handroanthus chrysanthus or Bursera
graveolens ), moderate canopy cover, and regeneration of few species
compared to natural forest. This state results from a history of land
use favouring few species followed by a transition from
shrub-dominated forest when livestock have been removed.
- Arid land: Nearly complete absence of woody species except
for isolated trees and shrubs. Herbaceous species comprise the only
stratum and are highly seasonal, proliferating in the rainy season.
Regeneration is low to absent and the soil is highly exposed and
eroded. This state results from a transition from shrub-dominated
forest when extensive livestock grazing and logging are practiced
continually over time.