NEWS
Not everything needs
to be a forest
Too often viewed as degraded forests rather than valuable grasslands, savannas are
threatened by carbon-storing afforestation programs that might not even work.
Reprinted From: http://bit.ly/37tiK1t
Brandon Keim
I
t was in Africa’s savannas that humani-
ty’s ancestors evolved to walk upright—
yet these savannas are threatened by
a human-dominated age, one in which
they’re officially designated as degraded
forests and scheduled for replacement.
The plight of savannas is the subject of
two recent papers, one about Asia and
one about Africa, but both sharing an
essential concern: that people are quick
to see tree-dotted grassy plains as mere
ecological placeholders for the forests
that ought to be there.
“Asian savannas have been misinter-
preted as degraded forest since the co-
lonial period,” write Dushyant Kumar, an
ecologist at Germany’s Senckenberg Bi-
odiversity and Climate Research Centre,
and colleagues in the journal Biological
Conservation. “There is an urgent need
for a correct interpretation.”
Tropical savannas presently cover about
one-fifth of Earth’s land surface, write Ku-
mar’s team, but they are threatened. By
suppressing naturally-occurring fire and
eradicating shrub-munching large her-
bivores, people have allowed forests to
encroach.
Savannas are also the target of affores-
tation programs that promise to seques-
ter carbon in newly-grown forests—but
whether these will work as intended is a
subject of ongoing scientific debate, and
“these agendas may omit the potential
negative consequences for biodiversity.”
The researchers modeled the vegetative
future of South Asia’s savannas from now
until the century’s end under a variety
of climate scenarios. Forest area is ex-
pected to increase by about 44 percent;
grasslands are expected to contract by
nearly 40 percent. And that’s not even
taking into account climate-oriented af-
19
forestation projects. “The continuous ef-
fort to afforest savanna areas poses ma-
jor threats to their biodiversity,” write the
researchers, depriving species adapted
to savanna life of their only home. “Eco-
system management policies in South
Asia should adopt a grass-centric per-
spective and prioritize grassland and sa-
vanna conservation.”
Their sentiments are echoed in the jour-
nal Trends in Ecology & Evolution, where
researchers led by biologist William
Bond of the University of Cape Town la-
ment that one million square kilometers
of African savanna—an area roughly the
size of France and Germany combined—
is now targeted for so-called restoration
by the year 2030.
“The target is based on the erroneous
assumption that these biomes are de-
forested and degraded,” they write.
Among the landscapes formally mapped
as degraded are the ancient savanna
landscapes of the Serengeti and Kruger
National Park, which have not been for-
ests for several million years.
More than a billion dollars have already
been pledged by Germany and the
World Bank; 28 African countries have
signed up for the AFR100, an offshoot
of the Bonn Challenge, the international
forest restoration and carbon sequestra-
tion initiative launched in 2011 with a
goal of putting trees on 3.5 million square
kilometers by 2030. Yet Bond’s team, like
Kumar’s, also points to growing scientific
debate over the climate impacts of af-
forestation—especially if new growth is,
as will likely be the case in Africa, planta-
tions rather than diverse forests.
They highlight recent research suggest-
ing that the Bonn Challenge’s 3.5 million
square kilometers would, if covered by
natural forests, sequester 42 gigatons
of carbon, but that figure falls to a mere
1 gigaton if the forests are the pine and
eucalyptus plantations expected in much
of Africa.
Forests may also absorb more solar ra-
diation than do grasslands, thus offset-
ting the extra carbon they store. And
when eucalyptus and pine plantations,
which are particularly vulnerable to high-
severity fires, burn, most of the carbon
they store is released back into the at-
mosphere.
In grasslands, argues Bond’s team, most
carbon is stored below ground and per-
sists through fire. “Converting African
savannas to plantations is pointless as a
mitigation measure,” they write.
Bond’s team stresses that truly degraded
forests ought to be restored and exist-
ing forests protected. But large-scale
afforestation “is based on the wrong as-
sumptions,” they argue. “Far from be-
ing deforested and degraded, Africa’s
savannas and grasslands existed, along-
side forests, for millions of years.”
Rather than covering them with trees,
people might “promote energy efficient
cities in this rapidly urbanizing continent
so that Africa follows a less carbon-in-
tensive trajectory of development than
other emerging economies.”
Sources
Bond et al. “The Trouble with Trees: Af-
forestation Plans for Africa.” Trends in
Ecology & Evolution, 2019.
Kumar et al. “Misinterpretation of Asian
savannas as degraded forest can mislead
management and conservation policy
under climate change.” Biological Con-
servation, 2019.
Grassroots
Vol 20
No 1
March 2020