The legacy of past human land use in current patterns of mammal distribution

Abstract

Multiple environmental factors are known to shape species distributions at the global scale, including climate and topography, but understanding current extents of occurrence and biodiversity patterns requires considering anthropogenic factors as well. Numerous studies have explored the relationship between contemporary human activities and different biodiversity metrics, but the influence of past activities, such as land‐use, remains poorly understood despite being one of the oldest human impacts. Here we evaluate the role of past land‐use modifications in the current distribution and conservation status of mammals worldwide using spatial data characterizing human land use from ca BC 6000 to ca AD 2000. First, we applied a clustering method that revealed three generalized past human land‐use trajectories that represent low‐, recently‐ and steadily‐used areas widely represented across the globe. Second, we fitted boosted regression trees to predict total and threatened mammalian richness, globally and within trajectory‐clusters, testing the role of environmental factors and multiple human land‐use metrics reflecting: total used area at different time spans, rates of land‐use change, and the occurrence of remarkable land‐use shifts. Environmental factors were identified as the main correlates of current mammalian richness, but several proposed metrics of past land‐use were also relevant predictors. Overall, these results highlight the likely existence of a land‐use legacy in some regions of the world that has influenced the distribution of extant mammals, particularly of those currently classified as threatened. Even if we cannot change that legacy, our results show that we need to account for past human impacts to understand present biodiversity patterns and, arguably, to guide future actions.

Current climate, but also long‐term climate changes and human impacts, determine the geographic distribution of European mammal diversity

“…Importantly, they have changed current diversity patterns (Faurby & Svenning, 2015), highlighting the importance of including human-related effects in large-scale studies focusing on diversity drivers. These human impacts are not restricted to post-industrial times (Polaina, González-Suárez, & Revilla, 2019).…”

“…Importantly, they have changed current diversity patterns (Faurby & Svenning, 2015), highlighting the importance of including human‐related effects in large‐scale studies focusing on diversity drivers. These human impacts are not restricted to post‐industrial times (Polaina, González‐Suárez, & Revilla, 2019). Instead, humans have long been an important driver of species range contractions and extinctions (Sandom, Faurby, Sandel, & Svenning, 2014).…”

Global biogeographical regions reveal a signal of past human impacts

“…The mammalian distributions that we know today are not only a reflection of the most recent human actions but also those exerted during the last few millennia 27,28 . Recent studies had already shown that human actions in the present can be evident at biogeographical scales 18,19 , but here we also show evidence of an effect of past human land use.…”

Land Use and Ecological Change: A 12,000-Year History

“…These differential and lagged responses are characterized as extinction debt when extinctions lag behind land use changes, such as when long-lived tree species lose their pollinators or seed dispersers, and as extinction filtering when the most vulnerable species are lost early, leaving communities of species better adapted to dynamic cultural landscapes and therefore less vulnerable to future changes (179). As a result of extinction debt and filtering, land use changes of the past, and their evolutionary consequences, can play a critical role in shaping current and future rates of extinction (127,129,130). low-tillage practices are introduced (88,118).…”

“…Deforestation and reforestation can both increase and decrease streamflow (126). The evolutionary consequences of early land use, including burning, habitat fragmentation, population declines in prey and other species, and the adaptations of remaining species to cultural landscapes, can produce legacy effects that can lower and/or obscure future rates of extinction through extinction filtering and extinction debt, respectively, while also shaping diverse and resilient novel communities and ecosystems (19,27,39,98,99,(127)(128)(129)(130); see also the sidebar titled Extinction Filtering and Extinction Debt). Given these complex, divergent, and often opposing ecological consequences, detailed reconstructions of long-term land use histories are essential to better understand the legacies of past land use and to enable more effective environmental governance in the future.…”