No abstract

Given the proliferation of primary research articles, the importance of reliable environmental evidence reviews for informing policy and management decisions is increasing. Although conducting reviews is an efficient method of synthesising the fragmented primary evidence base, reviews that are of poor methodological reliability have the potential to misinform by not accurately reflecting the available evidence base. To assess the current value of evidence reviews for decision-making we appraised a systematic sample of articles published in early 2015 (N=92) using the Collaboration for Environmental Evidence Synthesis Assessment Tool (CEESAT). CEESAT assesses the methodology of policy-relevant evidence reviews according to elements important for objectivity, transparency and comprehensiveness. Overall, reviews performed poorly with a median score of 2.5/39 and a modal score of zero (range 0-30, mean 5.8), and low scores were ubiquitous across subject areas. In general, reviews that applied meta-analytical techniques achieved higher scores than narrative syntheses (median 18.3 and 2.0 respectively), as a result of the latter consistently failing to adequately report methodology or how conclusions were drawn. However, some narrative syntheses achieved high scores, illustrating that the reliability of reviews should be assessed on a case-by-case basis. Given the potential importance of reviews for informing management and policy, as well as research, it is vital that overall methodological reliability is improved. Although the increasing number of systematic reviews and meta-analyses highlight that some progress is being made, our findings suggest little or no improvement in the last decade. To motivate progress, we recommend that an annual assessment of the methodological reliability of evidence reviews be conducted. To better serve the environmental policy and management communities we identify a requirement for independent critical appraisal of review methodology thus enabling decisionmakers to select reviews that are most likely to accurately reflect the evidence base.

Riparian forests are assumed to play a crucial role in the global carbon cycle. However, little data are available on C stocks of floodplains in comparison to other terrestrial ecosystems. In this study, we quantified the C stocks of aboveground biomass and soils of riparian vegetation types at 76 sampling sites in the Donau‐Auen National Park in Austria. Based on our results and a remotely sensed vegetation map, we estimated total C stocks. Carbon stocks in soils (up to 354 t ha–1 within 1 m below surface) were huge compared to other terrestrial ecosystems. As expected, soils of different vegetation types showed different texture with a higher percentage of sandy soils at the softwood sites, while loamy soils prevailed at hardwood sites. Total C stocks of vegetation types were significantly different, but reflect differences in woody plant biomass rather than in soil C stocks. Mature hardwood and cottonwood forests proved to have significantly higher total C stocks (474 and 403 t ha–1, respectively) than young reforestations (217 t ha–1) and meadows (212 t ha–1). The C pools of softwood forests (356 t ha–1) ranged between those of hardwood/cottonwood forests and of reforestations/meadows. Our study proves the relevance of floodplains as possible C sinks, which should be increasingly taken into account for river management. Furthermore, we conclude that plant‐species distribution does not indicate the conditions of sedimentation and soil C sequestration over the time span of interest for the development of soil C stocks.

Roads facilitate development in remote forest regions, often with detrimental consequences for ecosystems. In the Congo Basin, unpaved logging roads used by timber firms, as well as paved and unpaved public roads, have expanded greatly. Comparing older (before 2003) and newer (2003-2018) road datasets derived from LandSat imagery, we show that road networks inside logging concessions in Central Africa have doubled in length since 2003, whereas roads outside concessions increased by 40%. We estimate that 44% of all roads within concessions were abandoned by 2018, following logging operations, whereas just 12% of roads outside concessions were abandoned. Yearly deforestation rates (2000-2017) near (<1 km) roads rose dramatically during the course of this study, and were highest for older roads, lowest for

Road networks are expanding in tropical countries, increasing human access to remote forests that act as refuges for biodiversity and provide globally important ecosystem services. Logging is one of the main drivers of road construction in tropical forests. We evaluated forest fragmentation and impacts of logging roads on forest resilience and wildlife, considering the full life cycle of logging roads. Through an extensive evidence review we found that for logging road construction, corridors between 3 and 66 m (median 20 m) width are cleared, leading to a loss of 0.6–8.0 percent (median 1.7%) of forest cover. More severe impacts are increased fire incidence, soil erosion, landslides, and sediment accumulation in streams. Once opened, logging roads potentially allow continued access to the forest interior, which can lead to biological invasions, increased hunting pressure, and proliferation of swidden agriculture. Some roads, initially built for logging, become converted to permanent, public roads with subsequent in‐migration and conversion of forest to agriculture. Most logging roads, however, are abandoned to vegetation recovery. Given the far‐reaching impacts of the roads that become conduits for human access, its control after the end of logging operations is crucial. Strategic landscape planning should design road networks that concentrate efficient forest exploitation and conserve roadless areas.

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.

Logging roads can trigger tropical forest degradation by reducing the integrity of the ecosystem and providing access for encroachment. Therefore, road management is crucial in reconciling selective logging and biodiversity conservation. Most logging roads are abandoned after timber harvesting; however, little is known about their long-term impacts on forest vegetation and accessibility, especially in Central Africa. In 11 logging concessions in the Congo Basin, we field-sampled a chronosequence of roads that, judging from satellite images, had been abandoned between 1985 and 2015. We assessed recovery of timber resources, tree diversity and above-ground biomass in three zones: the road track, the road edge (where forest had been cleared during road construction) and the adjacent logged forest. The density of commercial timber species <15 cm d.b.h. was almost three times higher in the road track (321 individuals ha−1) and edge (267) than in the logged adjacent forest (97). Over time, tree species diversity converged to a comparable level between roads and adjacent forests, along with an increase in canopy closure. The average width of forest clearing for road construction was 20 m, covering a total 0·76% of the forest area inside concessions. After 15 years following abandonment, road tracks had recovered 24 Mg ha−1 of above-ground woody biomass, which was 6% of that in the adjacent forest, while road edges had accumulated 167 Mg ha−1 (42%). Ten years after abandonment, roads were no longer penetrable by poachers on motorcycles. An exotic herb species was fully replaced by dominant Marantaceae that have even higher abundance in the adjacent forest. • Synthesis and applications. Our evidence of vegetation recovery suggests that logging roads are mostly transient elements in the forest landscapes. However, given the slow recovery of biomass on abandoned road tracks, we advocate both reducing the width of forest clearing for road construction and reopening old logging roads for future harvests, rather than building new roads in intact forests. Road edges seem suitable for post-logging silviculture which needs to be assisted by removing dominant herbs during the early years after abandonment while the road track is still accessible. (Résumé d'auteur

Ecosystem restoration is an important means to address global sustainability challenges. However, scientific and policy discourse often overlooks the social processes that influence the equity and effectiveness of restoration interventions. In the present article, we outline how social processes that are critical to restoration equity and effectiveness can be better incorporated in restoration science and policy. Drawing from existing case studies, we show how projects that align with local people's preferences and are implemented through inclusive governance are more likely to lead to improved social, ecological, and environmental outcomes. To underscore the importance of social considerations in restoration, we overlay existing global restoration priority maps, population, and the Human Development Index (HDI) to show that approximately 1.4 billion people, disproportionately belonging to groups with low HDI, live in areas identified by previous studies as being of high restoration priority. We conclude with five action points for science and policy to promote equity-centered restoration.