hide
Free keywords:
-
Abstract:
This paper, developed under the framework of the
RECCAP initiative, aims at providing improved estimates of
the carbon and GHG (CO2, CH4 and N2O) balance of continental
Africa. The various components and processes of
the African carbon and GHG budget are considered, existing
data reviewed, and new data from different methodologies
(inventories, ecosystem flux measurements, models, and
atmospheric inversions) presented. Uncertainties are quantified
and current gaps and weaknesses in knowledge and monitoring
systems described in order to guide future requirements.
The majority of results agree that Africa is a small sink of carbon on an annual scale, with an average value of −0.61±0.58 PgC yr−1. Nevertheless, the emissions of CH4
and N2O may turn Africa into a net source of radiative forcing
in CO2 equivalent terms. At sub-regional level, there is
significant spatial variability in both sources and sinks, due
to the diversity of biomes represented and differences in the
degree of anthropic impacts. Southern Africa is the main
source region; while central Africa, with its evergreen tropical
forests, is the main sink. Emissions from land-use change
in Africa are significant (around 0.32±0.05 PgC yr−1), even
higher than the fossil fuel emissions: this is a unique feature
among all the continents. There could be significant carbon
losses from forest land even without deforestation, resulting
from the impact of selective logging. Fires play a significant
role in the African carbon cycle, with 1.03±0.22 PgC yr−1
of carbon emissions, and 90% originating in savannas and
dry woodlands. A large portion of the wild fire emissions are
compensated by CO2 uptake during the growing season, but
an uncertain fraction of the emission from wood harvested
for domestic use is not. Most of these fluxes have large interannual
variability, on the order of ±0.5 PgC yr−1 in standard
deviation, accounting for around 25% of the year-toyear
variation in the global carbon budget.
Despite the high uncertainty, the estimates provided in this
paper show the important role that Africa plays in the global carbon cycle, both in terms of absolute contribution, and as a key source of interannual variability.
