It has long been observed that roads clear the way to deforestation in the tropics. Viewing deforestation scars in the Congo Basin from space, we can now model the impact roads have both inside and outside logging concessions.
For how long will the Congo forests be the relatively spared lung of the planet? At first sight, observing deforestation scars on satellite imagery over Central Africa suggests these are caused by slash-and-burn agricultural practices. Much of the rural population in Africa makes a humble living out of this fire-based shifting agriculture. However, a closer look reveals that roads are a major condition before deforestation takes place. In particular, many of the roads going through forests are built for logging. Ultimately, roads within concessions for the timber industry are driven by the consumption model of globalized and urban societies1. Writing in Nature Sustainability, Fritz Kleinschroth and colleagues2 reveal the pattern of roads in the entire Congo Basin as well as its changes over the past 15 years inside and outside logging concessions.
As intact forests continue to deplete, we are getting closer to irreversible changes to our planet, a major threat to our survival as a species3. The Congo Basin contains the second-largest continuous tropical forest in the world, next to the Amazon (mostly in Brazil) and the Southeast Asian archipelago (mostly in Indonesia). Agroindustry for regional and global markets (especially bovine meat and soya) greatly contributed to the world-record deforestation rate in the Brazilian Amazon4. Forest plantations (palm oil and rubber industry) are a major cause for the increasing deforestation in Indonesia. In those regions, selective logging (felling trees of targeted species within the forest) usually took place before agroindustrial exploitation. Logging helped embrace local business partnerships and cheap labour that would then facilitate such exploitation.
By contrast, forest loss in the Congo Basin has long been considerably less than in these other regions5. The only large-scale activity with visible, extended impact on forest cover has been selective logging under forest concession schemes. Until recently, land under concessions expanded in most countries except the Democratic Republic of Congo (DRC), which accounts for over half of the Congo Basin forests. Long periods of civil war and higher economic instability in DRC had deterred international investment. Road building due to selective logging was reported to accelerate degradation and loss of intact forests of the Congo Basin6,7. However, recent studies hinted that sustainable logging-management plans may have successfully limited deforestation in the region8. To better understand current impacts of human activities inside and outside forest concessions, more comprehensive studies on forest cover are needed.
Kleinschroth and colleagues documented and analysed, for the first time, the road network within forests in the entire region of the Congo Basin. The authors downloaded and validated a large dataset of volunteered geographic information on the Internet, and they updated it to the year 2018 using visual detection of roads on satellite imagery. Then, using software for cartographic analysis, they documented the pattern of existing roads in the year 2003 and measured their evolution over the subsequent 15 years. Next, they incorporated the maps of yearly forest-cover loss for the Congo Basin, from Global Forest Watch, in the cartographic analysis.
The authors found that the road network doubled in size from 2003 to 2018 inside logging concessions (from 50,300 km to 100,300 km). In the same period, the proportional increase in roads within forests outside concessions was remarkably less, being 40% (from 93,300 km to 130,500 km). This implies that concessioning land for timber extraction boosts road construction through forests, many of them categorized as intact forests. Nevertheless, there seems to be some forest recovery, since many of the roads built within forests between 2003 and 2018 were abandoned (did not appear on the 2018 satellite imagery). More specifically, roads built outside concessions are more persistent in the long run: 44% of the roads inside logging concessions were abandoned, but only 12% of those outside concessions were. In addition, deforestation within one kilometre of abandoned roads was much less than deforestation within one kilometre of persistent roads. Overall, they concluded that roads opened outside logging concessions are more prone to induce deforestation than those opened inside concessions.
Between 2003 and 2018, the net increase of roads has been 13% inside and 23% outside logging concessions. This could suggest that concessioning is a positive policy for Congo Basin forests. Nevertheless, this initial interpretation does not heed important factors. Additional large-scale extractive activities can emerge (such as the ones that emerged in Brazil and Indonesia), attracted by the influx of foreign capital due to these concessions. Also, illegal activities such as poaching are likely to occur in the secondary vegetation settings of abandoned logging roads, escaping the control of forest-management operators7. These activities greatly affect endangered species and threaten biodiversity worldwide9.
With this new dataset and analysis, Kleinschroth and colleagues open the way to model scenarios of the expansion of logging concessions, hence contributing to the important question of whether the spread of these concessions might worsen, or ameliorate, the fate of Congo Basin tropical forests.
Fuller, T. L. et al. Area 51, 340–349 (2019).
Kleinschroth, F. et al. Nat. Sustain. https://doi.org/10.1038/s41893-019-0310-6 (2019).
Steffen, W. et al. Science 347, 1259855 (2015).
Tyukavina, A. et al. Sci. Adv. 3, e1601047 (2017).
Turubanova, S., Potapov, P. V., Tyukavina, A. & Hansen, M. C. Environ. Res. Lett. 13, 074028 (2018).
Laporte, N. T., Stabach, J. A., Grosch, R., Lin, T. S. & Goetz, S. J. Science 316, 1451 (2007).
Kleinschroth, F., Healey, J. R. & Gourlet‐Fleury, S. Front. Ecol. Environ. 14, 9–10 (2016).
Kleinschroth, F., Garcia, C. & Ghazoul, J. Ambio 48, 153–159 (2019).
Nature’s Dangerous Decline ‘Unprecedented’; Species Extinction Rates ‘Accelerating’ (IPBES, 2019); https://www.ipbes.net/news/Media-Release-Global-Assessment
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Couturier, S. The global scar on Congo forests. Nat Sustain 2, 547–548 (2019). https://doi.org/10.1038/s41893-019-0315-1
Impact of temporal variations in vegetation optical depth and vegetation temperature on L-band passive soil moisture retrievals over a tropical forest using in-situ information
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