Abstract:
Agricultural expansion has resulted in both land use and land cover change (LULCC) across the tropics. However,
the spatial and temporal patterns of such change and their resulting impacts are poorly understood, particularly for
the presatellite era. Here, we quantify the LULCC history across the 33.9 million ha watershed of Tanzania’s Eastern
Arc Mountains, using geo-referenced and digitized historical land cover maps (dated 1908, 1923, 1949 and 2000). Our
time series from this biodiversity hotspot shows that forest and savanna area both declined, by 74% (2.8 million ha)
and 10% (2.9 million ha), respectively, between 1908 and 2000. This vegetation was replaced by a fivefold increase in
cropland, from 1.2 million ha to 6.7 million ha. This LULCC implies a committed release of 0.9 Pg C (95% CI: 0.4–
1.5) across the watershed for the same period, equivalent to 0.3 Mg C ha
1 yr
1. This is at least threefold higher than
previous estimates from global models for the same study area. We then used the LULCC data from before and after
protected area creation, as well as from areas where no protection was established, to analyse the effectiveness of
legal protection on land cover change despite the underlying spatial variation in protected areas. We found that,
between 1949 and 2000, forest expanded within legally protected areas, resulting in carbon uptake of 4.8 (3.8–5.7)
Mg C ha
1, compared to a committed loss of 11.9 (7.2–16.6) Mg C ha
1 within areas lacking such protection. Furthermore,
for nine protected areas where LULCC data are available prior to and following establishment, we show that
protection reduces deforestation rates by 150% relative to unprotected portions of the watershed. Our results highlight
that considerable LULCC occurred prior to the satellite era, thus other data sources are required to better understand
long-term land cover trends in the tropics.
Description:
Global Change Biology,2016) 22, 2787–2800,
