Shrub encroachment occurs near previously invaded areas in Patagonia (southern South America).

PAULA ESTELÍ ROMERO OVALLE; MARÍA VICTORIA CAMPANELLA; MIGUEL PASCUAL; MARTÍN GARCÍA-ASOREY; CRISTINA PACHECO; CRISTIAN BARRIONUEVO; ALEJANDRO JORGE BISIGATO

LAND DEGRADATION & DEVELOPMENT

JOHN WILEY & SONS LTD

Lugar: LOndres; Año: 2023

1085-3278

Duringthe last century shrub encroachment has occurred in many arid and semiaridareas of the world. Patagonia is a large xeric territory located in thesouthern tip of South America, which has been grazed by sheep for more than acentury. In many areas overgrazing led to vegetation change (shrubencroachment), which in turn reduced sheep carrying capacity and caused ranchabandonment. However, these changes in physiognomy did not occur everywhere,and even some authors did not find evidence that shrub encroachment iscurrently occurring. Our objectives were to determine if encroachment reallyhappened in NE Patagonia and, in the case of confirming shrub encroachment, toevaluate if the increase in shrub density was spatially homogeneous. We usedobject- based image analysis (OBIA) to evaluate shrub density and cover inaerial photographs taken in 1970 and 2018. In both dates shrub density showed a clear contrastbetween two kinds of areas showing higher and lower density than was expectedby chance.Shrub density and cover more than doubled between 1970 and 2018. This increasewas concentrated in those areas with moderate or high densities of shrubs in1970. Our results confirm the occurrence of shrub encroachment in NE Patagoniaand demonstrate that it is currently concentrated near previously invaded areas.These findings have implications when defining protocols for monitoring shrubencroachment, since monitors should focus on both areas that already have shrubs and areas thatlack them