NEWS
Large mammals for a
better climate
Joris Cromsigt
E-mail Address: [email protected]
Reprinted From: http://bit.ly/2KeO8qM
R
estoring populations of large mam-
mals in the wild does not only revi-
talise the flora and fauna. It can also
help in mitigating climate change, for
example by increasing the capture of
carbon by ecosystems. This is the con-
clusion of ecologists representing sev-
eral universities, including Utrecht Uni-
versity, in a synthesis of existing studies.
The researchers published their results
in Philosophical Transactions of the Roy-
al Society B.
During the first half of the twentieth
century, the number of wildebeest in
the Serengeti plummeted to an all-time
low as a result of widespread rinderpest.
From 1960 the wildebeest population
began to increase once more, and their
grazing and trampling led to increased
soil productivity and a reduced inci-
dence of savanna wildfires.
An American study showed that the ef-
fect of this was so strong that the return
of the wildebeest resulted in the area
turning into a CO 2 sink. Where the vast
plains had once been a source of CO 2
emissions, the area now absorbs more
CO 2 than it emits, so much so that it off-
sets a great deal of East Africa's annual
fossil fuel carbon emissions.
Restoration of mammal populations
The loss of historical megafauna – mam-
mals weighing more than 40 kg – is being
increasingly connected with large-scale
changes in how the Earth functions. ‘Re-
wilding’ is the restoration of ecological
functions in an area by reintroducing re-
cently lost or restoring strongly reduced
populations of these large mammals.
In this synthesis, ecologists from Utrecht
University, the Swedish University of Ag-
ricultural Sciences (SLU), Nelson Man-
dela University and the University of
New Mexico present several strong ex-
amples that show a positive connection
between rewilding and climate change
mitigation, such as the capture of large
amounts of CO 2 by ecosystems.
Large animals disperse large seeds
“Another striking example is the role
of megafauna in the dispersal of seeds
from tropical hardwoods”, explains As-
sociate Prof Joris Cromsigt, ecologist
at Utrecht University and SLU and first
author of the publication. “The harder
the wood of a tree, the more carbon the
tree captures. But the harder the wood,
the larger the seed, and the greater the
tree's dependence on megafauna for
seed dispersal. Recent research shows
that the loss of large mammals could be
responsible for a 10% reduction in car-
bon capture in tropical forests in certain
parts of the world. The restoration and
conservation of tropical forests is one
of the frequently mentioned strategies
for combating global warming, and it
seems that rewilding of the tropical for-
ests can significantly increase the effec-
tiveness of this restoration.”
Reindeer counteract thawing of per-
mafrost
Cromsigt mentions a third example: “In
the northern latitudes a great deal of
carbon is stored in permafrost. Under
global warming the permafrost is thaw-
ing, which releases a substantial amount
of greenhouse gases.
One of the effects of warming is that
shrubs are increasingly encroaching on
the tundra, and these darker shrubs ab-
sorb more solar heat than grass, which
is leading to accelerated thawing of the
permafrost and more warming.
Northern megafauna, such as the rein-
deer, musk ox and Przewalski's horse
can inhibit this shrubification of the tun-
dra. So reintroducing these mammals
here can also contribute to fighting
global warming.”
Publication
Trophic rewilding as a climate change
mitigation strategy?
Joris P. G. M. Cromsigt*, Mariska te
Beest*, Graham I. H. Kerley, Marietjie
Landman, Elizabeth le Roux, Felisa A.
Smith
Figure 1: Grazing wildebeest on the Serengeti Savannah
Grassroots
Vol 18
No 4
December 2018
Philosophical Transactions of the Royal
Society B, 2018 * from Utrecht University
14