Legacy of logging roads in the Congo Basin: How persistent are the scars in forest cover?

Abstract

Abstract. Logging roads in the Congo Basin are often associated with forest degradation through fragmentation and access for other land uses. However, in concessions managed for timber production, secondary roads are usually closed after exploitation and are expected to disappear subsequently. Little is known about the effectiveness of this prescription and the factors affecting vegetation recovery rate on abandoned logging roads. In a novel approach we assessed logging roads as temporary elements in the forest landscape that vary in persistence depending on environmental conditions. We analyzed road persistence during the period 1986-2013 in adjacent parts of Cameroon, Central African Republic and Republic of Congo. Three successive phases of road recovery were identified on LANDSAT images: open roads with bare soil, roads in the process of revegetation after abandonment and disappeared roads no longer distinguishable from the surrounding forest. Field based inventories confirmed significant differences between all three categories in density and richness of woody species and cover of dominant herbs. We used dead-end road segments, built for timber exploitation, as sampling units. Only 6% of them were identified as being re-opened. Survival analyses showed median persistence of four years for open roads before changing to the revegetating state and 20 years for revegetating roads before disappearance. Persistence of revegetating roads was 25% longer on geologically poor substrates which might result from slower forest recovery in areas with lower levels of soil nutrient content. We highlight the contrast amongst forests growing on different types of substrate in their potential for ecosystem recovery over time after roads have been abandoned. Forest management plans need to take these constraints into account. Logging activities should be concentrated on the existing road network and sites of low soil resource levels should be spared from business-as-usual exploitation.

The Potential of Sentinel Satellites for Burnt Area Mapping and Monitoring in the Congo Basin Forests

“…The network of logging roads in the study area [30,31] is used as a proxy of human accessibility to the forest and related risk of human induced fire outbreak. In concessions managed for timber production, secondary roads are usually closed after exploitation and a rapid regrowth of vegetation is observed after abandonment.…”

“…In concessions managed for timber production, secondary roads are usually closed after exploitation and a rapid regrowth of vegetation is observed after abandonment. Kleinschroth et al, [30] observed a median persistence of four years for open roads before reverting to a vegetated state and 20 years before complete disappearance (no longer distinguishable from the surrounding forest).…”

Road Expansion and the Fate of Africa's Tropical Forests

“…In the Congo Basin alone, the Ouesso-Bangui-N'Djamena, Libreville-Lomie, Cameroon-Chad, and Northern Upgrade Corridors will span parts of Cameroon, Gabon, Republic of Congo, Democratic Republic of Congo, and Central African Republic (Laurance et al, 2015a). At present, many forests in these nations are still remote and only partially accessible via logging roads and existing timber concessions (Laporte et al, 2007;Kleinschroth et al, 2015). Unless environmental safeguards are rapidly implemented, the spate of new infrastructure projects will open up large tracts of Central Africa to further pressures, such as mining, hunting, logging, and deforestation for agriculture (Laurance et al, 2006(Laurance et al, , 2015aBlake et al, 2007;Poulsen et al, 2009).…”

“…These projects include a large number of industrial mining projects ; over 53,000 km of proposed "development corridors" (see some examples in Figure 1) that would crisscross much of the continent (Weng et al, 2013;Laurance et al, 2015a); the world's largest hydropower-dam complex, at Inga Falls on the Congo River; ambitious plans to increase industrial and smallholder agriculture (African Agricultural Development Company Ltd., 2013;Laurance et al, 2014a,b); widespread industrial logging (Laporte et al, 2007;Kleinschroth et al, 2015Kleinschroth et al, , 2016a; and a variety of other mining ventures and energy infrastructure with accompanying roads.…”

How persistent are the impacts of logging roads on Central African forest vegetation?

“…On Landsat images, they are detectable with bare soil for an average of 4 years and covered with vegetation for 20 years before they are no longer distinguishable from surrounding forest (Kleinschroth et al . ). Only 12% of roads in forest concessions observed over the last 15 years have been permanently open (Kleinschroth, Healey & Gourlet‐Fleury ).…”