Deforestation since independence: a quantitative assessment of four decades of land-cover change in Malawi

<p>Land cover has changed rapidly across the tropics over the past century; however, detailed historical information describing the extent and possible drivers of such change is widely lacking. Here, we constructed a history of land-cover change at the district level in Malawi over a 37-year period from 1972 to 2009, the immediate post-colonial phase. Overall, there was a loss of 12 760 km2 (36%) of original forested area but also 11 161 km2 of new forest establishment, resulting in a relatively modest overall net loss of 1 599 km2 (5%). We correlated changes in deforestation and forest establishment with changes in socio-economic variables derived from spatially explicit data from the same time period. Deforestation was positively correlated with (in order of influence) changes in male school attendance, sex ratio, population density, hospital bed numbers, protected areas and dependency rate, but negatively correlated with changes in cattle density; forest establishment broadly showed the inverse relationships with the same variables. Although direct drivers of deforestation are well known for Malawi and much of Africa, the significance of socio-economic variables within this study can help to understand the underlying social pressures behind such drivers. In particular, development, population pressure and demographic factors are important predictors of deforestation rate within our study area.</p

National forest trends in East Africa.

<p>Shown are overall forest trends independent of protection status (a) and forest trends depending on protection status (b). Note that only Kenya, Tanzania, Uganda, Rwanda and Burundi are fully covered by the study area.</p

Number of parks per category and country.

PC<p>country only partially covered in the East African study area.</p><p>Countries differ strongly with regard to presence and abundance of parks in the different protection categories. For example, Nature Reserves (NR) are only present in three countries.</p

Satellite-derived estimates of forest trend within and around three PAs in East Africa.

<p>Forest cover increased (green), decreased (red) or remained constant (orange). Some parks show significant loss in forest cover within their three buffer zones (0–1 km, 1 to 5 km, and 5–10 km). Other land cover transitions are white.</p

Trends in forest cover across protection categories between 2001 and 2009.

<p>Shown are the number of parks experiencing forest loss (<i>Ineffective</i> PAs) and the number of parks experiencing no change or an increase in forest cover (<i>Effective</i> PAs). Values in brackets show the mean area of forests (± standard error; in km²). <i>Ineffective</i> PAs were further divided into parks that lost more than or less than half their forest cover between 2001 and 2009.</p

Forest trends within individual parks of four different protection categories between 2001 and 2009 as function of initial forest size in 2001 (log10-scale).

<p>For graphical display of forest trends we excluded (very small) PAs that increased their forests by more than 300%. Thus, we excluded five Forest Reserves: Mukugodo FR in Kenya (3.9 km², 822%; forest cover in 2001 and forest change), Ngaia FR in Kenya (0.2 km², 900%), Geita FR in Tanzania (0.2 km², 600%), Vumari FR in Tanzania (0.6 km², 433%), Mwalugulu FR in Tanzania (0.4 km², 450%). On this basis, we also excluded four National Parks: Rubondo NP in Tanzania (0.4 km², 800%), Murchison Falls NP in Uganda (14.5 km², 391%), Mago NP in Ethiopia (0.4 km², 3550%) and Ruma NP in Kenya (1.1 km², 440%).</p

Percentage of forest change in buffer zones around PAs between 2001 and 2009.

<p><b>Buffer zones</b>: B01: zero to one km from park boundary, B15: one to five km from park boundary, B510: five to 10 km from park boundary. <b>Cell entries</b>: Mean values (± standard error) of forest change rates across parks within protection categories are shown (Number of parks in brackets). Note that parks were merged if they were located closer than 10 km from one another.</p

Forest trends in buffer zones (B01, B15, and B510) around <i>Effective</i> National Parks (i.e. parks that increased or maintained their forest area between 2001 and 2009).

<p><b>Numbers in bold represent the WDPA Identifier. 756</b>: Aberdare, Kenya (est. 1950), <b>779</b>: Nyika, Malawi (est. 1965), <b>922</b>: Kilimanjaro, Tanzania (est. 1973), <b>926</b>: Gombe, Tanzania (est. 1968), <b>2296</b>: Ruma, Kenya (est. 1983), <b>9162</b>: Rusizi, Burundi (est. 1980), <b>NP1</b>: merged parks 925 (Arusha, Tanzania, est. 1960) and 303328 (Meru, Tanzania, est. 1951), <b>NP5</b>: merged parks 9148 (Nyungwe, Rwanda, est. 1933) and 9161 (Kibira, Burundi, est. 1934), <b>NP6</b>: merged parks 863 (Volcans, Rwanda, est. 1929), 18438 (Rwenzori Mountains, Uganda, est. 1991), 40002 (Kibale, Uganda), 40042 (Semuliki, Uganda, est. 1993), 313109 (Mgahinga Gorilla, Uganda, est. 1930), 166889 (Parc National des Virunga, Congo) and 957 (Queen Elizabeth, est. 1952).</p><p>N with forest – Number of parks that encompassed evergreen forests in this buffer zone; N (FL) – Number of parks with forest loss in that buffer zone; N (FL > FLBG) – Number of parks with forest loss (FL; in %) that was higher than background forest loss (FLBG; in %) outside protected areas in East Africa; Parks (FL > FLBG) – name of parks with FL > FLBG). See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039337#pone-0039337-t003" target="_blank">Table 3</a> for further details on buffer zones.</p

Significant drivers of forest trends (0: no forest loss, 1: forest loss) modelled using general linear models with logit link functions.

<p>Numbers in brackets give the mean and standard error of the coefficient; associated <i>P</i> values are given at *<i>P</i><0.05,</p>**<p><i>P</i><0.01,</p>***<p><i>P</i><0.001).</p><p>We computed deforestation models for East Africa (Model 1) and for a subset of the study area (Model 2) because geographic data on the spatial location of towns and roads were available for the countries listed in Model 2 only <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039337#pone.0039337-FAO2" target="_blank">[58]</a>. ‘Protection Status’ is treated as categorical variable with the terms: Game Parks, Not Protected, National Parks, Nature Reserves, Other Protection). A subsequent Wald Chi-Squared test indicates that the overall effect of Protection Status is statistically significant (<i>P</i><0.0001). Abbreviations: likelihood ratio (LR), McFadden’s pseudo R² (Pseudo-R), Akaike Information Criterion (AIC) and significance of model (<i>P</i>).</p

Changes in human population densities with increasing distance from parks across the study area in East Africa.

<p>Patterns of human population densities within buffer zones of protected areas differ between protection categories.</p