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Changes in land cover in the Miombo-Mopane landscape in Tanzania
Background
The Central Zambezian Miombo woodlands cover 93% of Tanzania’s forested land. Miombo woodlands are a global biodiversity hotspot with irreplaceable endemism. The mosaic of Mopane/Miombo woodlands fulfil various ecosystem services supporting the resilience of surrounding farmland and communities, especially under climate change.
This unique ecosystem is increasingly being degraded by shifting cultivation with inadequate rotational fallow periods, overgrazing, charcoal production and uncontrolled fires. Irregular rainfalls are further increasing the negative effects of these practices. Land productivity is therefore decreasing while the population is rapidly increasing.
This story shows how Earth Map can support project designers to define an area of intervention in the context of a development programme such as the Drylands Impact Programme of the Global Environmental Facility (GEF). In this case, a watershed approach was used. First of all a Sub-basin (Mlele) was identified and existing remote sensing products embedded in Earth Map were used to describe their main features and characteristics.
Region
Tanzania, East Africa
Topic
Land Use Change, Land Degradation, Fires
Findings
The vegetation, fire and land use change data we assessed show how drivers of land degradation such as shifting cultivation or uncontrolled fires are affecting the area .The maps and statistics can help to identify an area that is in need of sustainable dryland management practices that could help to avert a deterioration of the observed situation.
The sub-basin (Figure 1) is located in the western part of the country and covers an area of 371 178.21 ha located entirely within the Mlele district. The area is also located among different reserves of ecological and touristic importance for the country;
A greenest-pixel mosaic of the area in 2000 and 2018 (Figure 2) clearly shows an extensive removal of tree cover. The deforestation front expands as small settlements become larger and more densely populated. The large deforestation patch in the north-west of the image is the town of Inyonga and the smaller one to the east is the town of Ilunde. This area has seen a population increase from 13 089 inhabitants in 2000 to 25 095 in 2015;
Changes in land cover over the years (Table 1) highlight strong correlation between the decrease in tree cover and increase in cropland area in the Sub-basin (Mlele). The Mlele district was formed in 2012 out of the Mpanda district and changes in land cover reflect this change: i.e. areas of forest land being cleared into grassland and cropland areas;
Fire occurrence and frequency is not evenly distributed in the area (Figure 3). Most fires occur in areas of forest land (darker shades represent higher annual frequency of fires). Population centres (where most continuous vegetation has been removed) are areas with the lowest occurrence of fires;
Burned area statistics (Figure 4) show that June, July and August are the months with the larger extent of burned areas. These are the months when precipitation in the region is very low.
Figure 1: Screenshot of the area of intervention: Sub-basin (Mlele).
Figure 2: Vegetation intensity with zoom-in to the sub-basin, images in 2000 and 2018 (based on Landsat - Greenest Pixel Yearly 1984-2018)
Table 1: Land cover change between 1995 and 2018 in Mlele sub-basin (based on European Space Agency (ESA) Land Cover CCI data).
Figure 3: Fire frequency map between 2001-2021) (based on MCD64A1 v006). Most fires occur in areas of forest land (darker shades represent higher annual frequency of fires). Population centres (where most continuous vegetation has been removed) are areas with the lowest occurrence of fires.
Figure 4: Graphics showing statistics on burned areas at the yearly and the monthly basis (based on MCD64A1 v006 and CHIRPS). The monthly average of burned area and precipitation is calculated for the last 19 years (between 2001 and 2019).