The effects of seaward distance on above and below ground carbon stocks in estuarine mangrove ecosystems

Mangrove forests have gained recognition for their potential role in climate change mitigation due to carbon sequestration in live trees, and carbon storage in the sediments trapped by mangrove tree roots and pneumatophores. Africa hosts about 19% of the world’s mangroves, yet relatively few studies have examined the carbon stocks of African mangroves. The available studies report considerable differences among sites and amongst the different pools of carbon stocks. None considered the effects of seaward distance. We present details of AGC and SOC carbon stocks for Lindi in Tanzania, and focus on how these values differ with increasing seaward distance and, how our results compare to those reported elsewhere across Africa

Environmental impacts of mining on biodiversity and ecosystem services

Mining is an important economic sector that ensures continuous flow of income, employment, and business opportunities. Mining furthermore can promote education, improve health facilities, and improve community infrastructure. However, mining often causes undesirable impacts on biodiversity and the ecosystem services they underpin. This thesis presents results from a systematic review of the mining literature, historical analysis of satellite imagery, field-based biodiversity assessments and interviews with a wide range of stakeholders involved in mining operations and communities living within mining areas. Combined, these different approaches assess the environmental impacts of mining on biodiversity, ecosystem services, and the potential for restoration of mining landscape across the globe, and land use and land cover change through time and across space in Tanzania. Results from the systematic review revealed that, out of 2,093 studies reviewed, 99.8%, reported some form of negative impact of mining on biodiversity and ecosystem services. However, while 95% reported on the direct impacts, only 5% reported on the indirect impacts. Furthermore, out of 830 reviewed restoration studies, most focused on remediation experiments (43.9%, n = 364) while 26.3%, n = 216 focused on reclamation, 14.9%, n = 124 focused on rehabilitation and 14.9%, n = 124 focused on restoration. Results also revealed that commercial gold mines have escalated the rate of land cover changes and pulled illegal mining adjacent to mine leases. This is associated with impacts that manifest largely outside operational boundaries. This was observed in two older mine sites, where aboveground carbon and tree stem density are significantly higher within lease boundaries compared to outside, while there is no such effect at the new site. I recommend on rigorous, integrated impact assessments and conservation planning in mining landscapes to mitigate social and environmental impacts and balance outcomes across the mining sector to support livelihoods, development, and conservation agendas

Implications of land use land cover change on the biodiversity of Kibasira swamp in Kilombero valley, Tanzania

MSc ThesisSustained wetland functioning needs proper land use planning which in its best requires integrated land management. High anthropogenic pressures on the Kibasira Swamp may undermine its potential in biodiversity conservation and ecosystem services provisioning. A study was conducted to investigate the implications of land use/cover on the biodiversity of Kibasira Swamp. Landsat TM and ETM+ images for the period 1990, 1998 and 2011 were used to quantify the changes. Plants and bird species were also assessed using nested plots of 0.08 ha and point count of 50 m radius respectively. The sampling points (plots) were established along 8 transects of 3 km radiating from the Swamp. Information from key informants was collected to assess the past status and trends in biodiversity of the Swamp. Results revealed a 1% and 4% increase in areas covered by water and forests respectively for the periods between 1990 and 1998 whilst Papyrus and cultivated areas decreased by 8% and 3%, respectively in the same period. For the period 1998 to 2011, there was a 35% and 9% decrease in areas covered by water and forests respectively while that of Papyrus increased by 40% and cultivated areas by 8%. Farmlands had higher bird species richness (76 species) than other habitats. However, the Swamp had higher abundance of birds (22 260 birds/km2) than other habitats. Furthermore areas with termite mounds had significantly higher tree species richness than surrounding areas (t = 1.68, P< 0.001). At least 15 tree species were found only in termite mounds. There is a strong evindence that land use/cover in the Kibasira swamp has changed substantially over time due to increasing athropogenic activities especially agriculture. This has resulted into a profound influence on the biodiversity of the Swamp. Measures to contain the anthropogenic activities that are a threat to the biodiversity of the Swamp and the Kilombero wetlands at large are inevitable

Forest Structure and Climate Change Mitigation Potential: A Case of Wilolesi and Ikonongo Forested Hills in Iringa Municipality, Tanzania

Vegetation plays major roles in carbon storage and ecosystem functioning by modifying the rate of carbon fluxes thereby mitigating climate change. However, the focus of assessing the potentials for different vegetation on climate change mitigation has for so long been conducted outside cities, towns and municipalities. This study was conducted in Wilolesi and Ikonongo hills located in Iringa as representative of the Municipality forested hills in Tanzania to assess vegetation structure and their potential for climate change mitigation. Random sampling technique was employed to establish 20 rectangular plots of 20 m x 40 m (0.08 ha) in each hill to determine plant species composition, richness, diversity, vegetation structure and above ground carbon (AGC). R-statistical software was used to compute Shannon-Wiener diversity indices, species richness and the above ground carbon. Results indicated high species diversity ranging from 3.5 to 4.1 for Ikonongo and Willolesi hills, respectively based on Shannon-Wiener diversity index (H’). We recorded 255 plant species (114 tree species, 51 shrub species, 2 sedge species, 66 herb species, 15 grass species and 7 climbers) in 60 families. Based on Important Value Index (IVI), Brachystegia spiciformis Benth (10.435) and Julbernardia globiflora Benth (4.555) were important species in Wilolesi and Ikonongo forested hills. There was a significant difference on the AGC between Ikonongo (3.12 t/ha) and Wilolesi (8.33 t/ha) (t = 1.83, p = &lt; 0.004). Results have an implication for dedicating more efforts on the management of forest landscapes for biodiversity conservation, climate change mitigation and provision of other ecosystem services. It is recommended that there should be detailed study for all forested hills in Iringa Municipality for proper forest management initiatives. Keywords: Climate change mitigation potential; forest structure; forested hill

Indirect impacts of commercial gold mining on adjacent ecosystems

Mining is important for economic development in many tropical countries, but mining can have serious impacts on biodiversity, both directly through operations at extraction sites, and indirectly via wider social-economic development. However, mitigation efforts by large-scale mining operators focus almost exclusively on extraction sites. We provide a rare assessment of mining impacts on vegetation structure and biodiversity with increasing distance from three commercial gold mines of varying ages in Tanzania (0 years, 8 years, and 19 years since establishment). We show that mining is associated with impacts that manifest largely outside operational lease boundaries. At the two older mine sites, aboveground carbon and tree stem density are significantly higher within lease boundaries compared to outside, while there is no such effect at the new site. Further, tree stem density, aboveground carbon, and tree and butterfly species richness all decrease with increasing distance from extraction sites, with these effects again increasing with mine age. Frugivorous bird species richness is lower outside older mines, while abundance declines in frugivorous and granivorous birds are associated with declines in tree stem density, which may have implications for forest regeneration. These impacts result from new and expanding settlements around mining concessions between 2000 and 2019 and associated demand for timber and fuelwood. We recommend rigorous, integrated impact assessments and conservation planning in mining landscapes, to pre-empt the development of settlements and secondary industries around mining sites and so balance outcomes across the mining sector, natural resource-based and other livelihoods, and conservation agendas

Indirect impacts of commercial gold mining on adjacent ecosystems

Mining is important for economic development in many tropical countries, but mining can have serious impacts on biodiversity, both directly through operations at extraction sites, and indirectly via wider social-economic development. However, mitigation efforts by large-scale mining operators focus almost exclusively on extraction sites. We provide a rare assessment of mining impacts on vegetation structure and biodiversity with increasing distance from three commercial gold mines of varying ages in Tanzania (0 years, 8 years, and 19 years since establishment). We show that mining is associated with impacts that manifest largely outside operational lease boundaries. At the two older mine sites, aboveground carbon and tree stem density are significantly higher within lease boundaries compared to outside, while there is no such effect at the new site. Further, tree stem density, aboveground carbon, and tree and butterfly species richness all decrease with increasing distance from extraction sites, with these effects again increasing with mine age. Frugivorous bird species richness is lower outside older mines, while abundance declines in frugivorous and granivorous birds are associated with declines in tree stem density, which may have implications for forest regeneration. These impacts result from new and expanding settlements around mining concessions between 2000 and 2019 and associated demand for timber and fuelwood. We recommend rigorous, integrated impact assessments and conservation planning in mining landscapes, to pre-empt the development of settlements and secondary industries around mining sites and so balance outcomes across the mining sector, natural resource-based and other livelihoods, and conservation agendas

REDD herrings or REDD menace: response to Beymer-Farris and Bassett

Norwegian funded REDD+ projects in Tanzania have attracted a lot of attention, as has the wider REDD+ policy that aims to reduce deforestation and degradation and enhance carbon storage in forests of the developing countries. One of these REDD+ projects, managed by WWF Tanzania, was criticised in a scientific paper published in GEC, and consequently in the global media, for being linked to attempted evictions of communities living in the Rufiji delta mangroves by the Government of Tanzania, allegedly to make the area ‘ready for REDD’. In this response, we show how this eviction event in Rufiji mangroves has a history stretching back over 100 years, has nothing to do with REDD+ or any policy changes by government, and is not in any way linked to the work of any WWF project in Tanzania. We also outline some of the broader challenges faced by REDD+ in Tanzani

Tropical forest canopies and their relationships with climate and disturbance : results from a global dataset of consistent field-based measurements

Background: Canopy structure, defined by leaf area index (LAI), fractional vegetation cover (FCover) and fraction of absorbed photosynthetically active radiation (fAPAR), regulates a wide range of forest functions and ecosystem services. Spatially consistent field-measurements of canopy structure are however lacking, particularly for the tropics. Methods: Here, we introduce the Global LAI database: a global dataset of field-based canopy structure measurements spanning tropical forests in four continents (Africa, Asia, Australia and the Americas). We use these measurements to test for climate dependencies within and across continents, and to test for the potential of anthropogenic disturbance and forest protection to modulate those dependences. Results: Using data collected from 887 tropical forest plots, we show that maximum water deficit, defined across the most arid months of the year, is an important predictor of canopy structure, with all three canopy attributes declining significantly with increasing water deficit. Canopy attributes also increase with minimum temperature, and with the protection of forests according to both active (within protected areas) and passive measures (through topography). Once protection and continent effects are accounted for, other anthropogenic measures (e.g. human population) do not improve the model. Conclusions: We conclude that canopy structure in the tropics is primarily a consequence of forest adaptation to the maximum water deficits historically experienced within a given region. Climate change, and in particular changes in drought regimes may thus affect forest structure and function, but forest protection may offer some resilience against this effect.Peer reviewe

Journal officiel de la Guinée française

01 septembre 19231923/09/01 (A23,N537)