Abstract:
Trophic rewilding aims to promote biodiverse self-sustaining ecosystems
through the restoration of ecologically important taxa and the trophic interactions
and cascades they propagate. How rewilding effects manifest across
broad temporal scales will determine ecosystem states; however, our understanding
of post-rewilding dynamics across longer time periods is limited.
Here we show that the restoration of a megaherbivore, the African savannah
elephant (Loxodonta africana), promotes landscape openness (i.e., various
measures of vegetation composition/complexity) and modifies fauna habitat
and that these effects continue to manifest up to 92 years after reintroduction.
We conducted a space-for-time floristic survey and assessment of 17 habitat
attributes (e.g., floristic diversity and cover, ground wood, tree hollows)
across five comparable nature reserves in South African savannah, where elephants
were reintroduced between 1927 and 2003, finding that elephant
reintroduction time was positively correlated with landscape openness and
some habitat attributes (e.g., large-sized tree hollows) but negatively associated
with others (e.g., large-sized coarse woody debris). We then indexed elephant
site occurrence between 2006 and 2018 using telemetry data and found positive
associations between site occurrence and woody plant densities. Taken
alongside the longer-term space-for-time survey, this suggests that elephants
are attracted to dense vegetation in the short term and that this behavior
increases landscape openness in the long term. Our results suggest that trophic
rewilding with elephants helps promote a semi-open ecosystem structure of
high importance for African biodiversity. More generally, our results suggest
that megafauna restoration represents a promising tool to curb Earth’s recent
ecological losses and highlights the importance of considering long-term ecological
responses when designing and managing rewilding projects.
