Megafauna in the Earth system

Abstract

Understanding the complex role of large‐bodied mammals in contemporary ecosystems and the likely consequences of their continued decline is essential for effective management of the remaining wild areas on Earth. The very largest animals are in particular peril owing to a disastrous combination of continued hunting or poaching, habitat alterations, and loss of habitat. Because these threats are ongoing, conservation biologists may not be able to wait for the results of long‐term studies before proposing potential mitigation strategies. A recent conference on ‘Megafauna and ecosystem function: from the Pleistocene to the Anthropocene’ at Oxford Univ. brought together paleontologists, conservation and environmental scientists and others who share an interest in characterizing the influence of large animals on ecosystems. Integrating historical perspectives of Late Pleistocene ecosystems when large‐bodied animals were still widespread, with modern studies of areas with varying levels of intact megafauna, the aim was to develop a more holistic understanding of the consequences of the ongoing decline of large‐bodied animals around the Earth. The conference resulted in the development of two special features – one in the Proceedings of the National Academy of Science, USA and one in Ecography synthesizing the state of our knowledge about the environmental legacies of the terminal Pleistocene megafauna extinction, the complex role of modern large‐bodied animals and what the ongoing loss of their ecological interactions might mean in terms of ecosystem function. Here, we briefly review the main themes developed during the conference and outline promising future research directions.

Freshwater megafauna diversity: Patterns, status and threats

“…Furthermore, many remaining megafauna species are experiencing range contractions and population declines (Malhi et al., ; Wolf & Ripple, ). This decline and loss of megafauna species and populations can have profound effects on local ecosystems, leading to altered habitat conditions for co‐occurring species, disruption of biogeochemical processes and loss of key ecosystem services (Estes, Heithaus, McCauley, Rasher, & Worm, ; Estes et al., ; Naiman, Bilby, Schindler, & Helfield, ; Smith, Doughty, Malhi, Svenning, & Terborgh, ). To date, research and conservation activities have predominantly focused on marine and terrestrial megafauna, neglecting those in freshwaters (Cooke et al., ; He et al., ).…”

The Rise of the Anthroposphere since 50,000 Years: An Ecological Replacement of Megaherbivores by Humans in Terrestrial Ecosystems?

“…In any case, this worldwide extinction led to a strong decrease of mean body mass of terrestrial mammals, almost symmetrical to the increase seen at the beginning of the Cenozoic (Smith et al, 2016b), only much faster, occurring in a few thousand years instead of a few million years. The ecological consequences of these extinctions are increasingly investigated (e.g., Bunzel-Drüke et al, 2001;Catling, 2001;Putshkov, 2003;Brault et al, 2013;McClure, 2013;Gill, 2014;Bakker et al, 2016;Doughty et al, 2016a).…”

The importance of ecological memory for trophic rewilding as an ecosystem restoration approach

“…Understanding the history of ecosystems is a prerequisite when planning restoration activities like trophic rewilding that aims for sustainable maintenance of biodiverse, functional ecosystems (Landres, Morgan & Swanson, 1999;Smith et al, 2016;Svenning et al, 2016). Most attributes observable in current ecosystems (e.g.…”

“…There may also be intermediate cases where re‐establishment is actively promoted without direct translocation of animals. In all cases, large‐bodied animals (megafauna) are assumed to have disproportionally large and beneficial effects on the biodiversity and functioning of ecosystems (Malhi et al, ; Smith et al, ; Fernández et al, ), and all are considered in our discussion of trophic rewilding below. If necessary, rewilding of large‐bodied herbivores can be complemented with the (re)introduction of predators when potential negative effects of herbivore (re)introduction (e.g.…”

“…To maximise the benefits and reduce potential ecological risks linked to trophic rewilding, we need a thorough understanding of the complex role of megafauna in ecosystem functioning (Smith et al, ). Case studies (e.g.…”