Mapping extinction debt highlights conservation opportunities for birds and mammals in the South American Chaco

Abstract

Habitat loss is the primary cause of local extinctions. Yet, there is considerable uncertainty regarding how fast species respond to habitat loss, and how time‐delayed responses vary in space. We focused on the Argentine Dry Chaco (c. 32 million ha), a global deforestation hotspot, and tested for time‐delayed response of bird and mammal communities to landscape transformation. We quantified the magnitude of extinction debt by modelling contemporary species richness as a function of either contemporary or past (2000 and 1985) landscape patterns. We then used these models to map communities' extinction debt. We found strong evidence for an extinction debt: landscape structure from 2000 explained contemporary species richness of birds and mammals better than contemporary and 1985 landscapes. This suggests time‐delayed responses between 10 and 25 years. Extinction debt was especially strong for forest specialists. Projecting our models across the Chaco highlighted areas where future local extinctions due to unpaid extinction debt are likely. Areas recently converted to agriculture had highest extinction debt, regardless of the post‐conversion land use. Few local extinctions were predicted in areas with remaining larger forest patches. Synthesis and applications. The evidence for an unpaid extinction debt in the Argentine Dry Chaco provides a substantial window of opportunity for averting local biodiversity losses. However, this window may close rapidly if conservation activities such as habitat restoration are not implemented swiftly. Our extinction debt maps highlight areas where such conservation activities should be implemented.

Importance of spatio–temporal connectivity to maintain species experiencing range shifts

“…Their effects on the relative importance of spatio-temporal connectivity, however, has yet to be fully understood. This issue has significance for conservation science, as it helps to identify conditions under which extinction debts are likely to occur in the landscape (Semper-Pascual et al 2018), and guides conservation practices to avoid eventual local extinctions. We found that the effect sizes of these three factors varied depending on species dispersal ability (Supplementary material Appendix 1 Fig.…”

“…These approaches have also been employed to evaluate the impacts of climate change on habitat connectivity and species persistence (Dilts et al 2016, Albert et al 2017, Rehnus et al 2018, Kanagaraj et al 2019. Most connectivity models rely on spatial snap-shots of landscape structure to generate static connectivity estimates; however, some species predicted to experience ARH decrease or increase do not actually have immediate population declines or growth as expected (Metzger et al 2009, Semper-Pascual et al 2018, Lira et al 2019). Such 'extinction debt' and 'colonization credit' phenomena (Tilman et al 1994, Lira et al 2019) require ecologists to consider temporal ecological processes going beyond a purely spatial perspective.…”

Influence of Anthropogenic Factors on the Diversity and Structure of a Dry Forest in the Central Part of the Tumbesian Region (Ecuador–Perú)

“…These factors are mainly responsible for loss of species (or reduced genetic variability); however, they can also increase the abundance of other species, thereby homogenizing the landscape and the ecosystem [10][11][12]. A clear instance of these effects was shown by Semper et al [8], who revealed the influence of land conversion on the richness of animals in Chaco, Argentina: the local extinction of birds and mammals here was estimated as 56% in areas recently turned to pastures, and 29% in areas converted to crop fields.…”

“…Tropical dry forests are well-known as important ecosystems, yet they are exposed to many threats [1][2][3][6][7][8][9], including deforestation, fragmentation, overgrazing, fire, conversion to agriculture, and drought. These factors are mainly responsible for loss of species (or reduced genetic variability); however, they can also increase the abundance of other species, thereby homogenizing the landscape and the ecosystem [10][11][12].…”

Effects of habitat fragmentation on the persistence of medium and large mammal species in the Brazilian Savanna of Goiás State

“…Delayed response is still largely unexplored in researches investigating the effects of natural habitat change on species, especially in Brazil. Researches on extinction debt carried out so far have primarily evaluated plants and birds, whereas mammals have rarely been the object of study (Semper-Pascual et al 2018). Thus, the objective of this study was to assess the implications of habitat loss on the persistence of medium and large mammal species, considering the spatial and temporal changes in the evaluated landscapes.…”