NEWS
cattle, sheep, antelope and giraffes pro-
duce considerably more methane than
non-ruminants such as elephants, hip-
pos and zebras. In addition, larger ani-
mals produce more methane per body
mass. The dominance of livestock in Af-
rica has resulted in a significant increase
in methane emissions – up to 15% of the
global emission levels.
6. Movement of nutrients
Animals move nutrients from nutrient
hotspots across ecosystems, thereby in-
creasing overall fertility. The dominance
of livestock has resulted in widespread
loss of nutrient dispersal – with current
levels estimated at being less than five
percent of previous levels.
7. Ecosystem susceptibility
Mesic habitats (those with a balanced
supply of moisture) have experienced
biomass losses while arid habitats have
experienced biomass increases.
The imposition on arid habitats of in-
creased livestock biomass (mostly
sedentary), is causing disturbance to
vegetation that usually has a seasonal
dynamic. For example, year-round tram-
pling and grazing may increase grass
tuft mortality and thereby increased soil
erosion by wind and water, and reduced
water infiltration due to soil compaction
and greater run-off.
The removal of elephants from mesic
habitats holds more substantial ecolog-
ical implications, by increasing woody
growth and reducing movement of nu-
trients in these typically highly leached,
nutrient poor ecosystems.
Humans are replacing some of this el-
ephant functionality by harvesting fuel-
wood, and currently woody biomass is
reducing over much of the continent,
despite the ongoing encroachment of
woody vegetation.
Human hunting is likely to remain the
greatest threat to large mammal herbi-
vores in Africa’s tropical forest ecosys-
tems, exacerbating current effects on
seed dispersal, recruitment and vegeta-
tion structure in the forest understory.
The general shift from migratory native
to resident livestock herbivore popula-
tions represents a ubiquitous distortion
of large mammal herbivore ecology.
Only a handful of ecosystems now re-
tain the diversity of functional seasonal
resources necessary to support large,
migratory herbivore populations that
can adapt to inherently variable ecosys-
tems.
Populations that cannot migrate are
more susceptible to drought and are
subject to considerable natural fluctua-
tion in herbivore densities.
The full report: Nature.com, Gareth P.
Hempson, Sally Archibald, William J.
Bond: “The consequences of replacing
wildlife with livestock in Africa“
Photo Competition Entry: Research in Action
Soweto Highveld Grassland biodiversity Research; Sasol/Secunda Photo: Wayne Matthews
Grassroots
Vol 19
No 4
November 2019
18