Inequitable gains and losses from conservation in a global biodiversity hotspot

A billion rural people live near tropical forests. Urban populations need them for water, energy and timber. Global society benefits from climate regulation and knowledge embodied in tropical biodiversity. Ecosystem service valuations can incentivise conservation, but determining costs and benefits across multiple stakeholders and interacting services is complex and rarely attempted. We report on a 10-year study, unprecedented in detail and scope, to determine the monetary value implications of conserving forests and woodlands in Tanzania’s Eastern Arc Mountains. Across plausible ranges of carbon price, agricultural yield and discount rate, conservation delivers net global benefits (+US$8.2B present value, 20-year central estimate). Crucially, however, net outcomes diverge widely across stakeholder groups. International stakeholders gain most from conservation (+US$10.1B), while local-rural communities bear substantial net costs (-US$1.9B), with greater inequities for more biologically important forests. Other Tanzanian stakeholders experience conflicting incentives: tourism, drinking water and climate regulation encourage conservation (+US$72M); logging, fuelwood and management costs encourage depletion (-US$148M). Substantial global investment in disaggregating and mitigating local costs (e.g., through boosting smallholder yields) is essential to equitably balance conservation and development objectives.</p

Population structure and carbon storage of critically endangered tree Karomia gigas (Faden) Verdic in the coastal forests of Lindi, Tanzania

Global biological loss is predominantly propelled by human activities resulting in the extinction of some important plant species while pushing others to the brink of critical danger. Better understanding of the ecology of these important species facilitates safeguarding their habitats and the development of sustainable restoration strategies. Data on vegetation, physiographic, edaphic and anthropogenic variables were collected from forty (40) concentric temporary circular plots in two forest reserves (i.e. Mitundumbea and Litipo Forest Reserves) to determine population structure and above-ground carbon storage of Karomia gigas (Faden) Verdic a critically endangered tree species in the coastal forests of Lindi, Tanzania. Within the Litipo Forest Reserve, we recorded a total of 30 K. gigas individual trees, comprising 13 seedlings, 10 saplings and 7 mature trees. The largest measured diameter at breast height (dbh) in this forest was 29.2 cm while the smallest was 0.9 cm. In contrast, the Mitundumbea Forest Reserve had 15 mature K. gigas individual trees but lacked seedlings and saplings. The largest dbh recorded in this forest stood at 59.7 cm, with the smallest dbh measurement being 5.1 cm. We overall observed significant negative correlations between the abundance of K. gigas adults and both soil organic carbon (P = 0.005) and burnt areas (P = 0.003). The total abundance of K. gigas showed a negative association with soil organic carbon (P = 0.011). Furthermore, the carbon storage of K. gigas exhibited a negative relationship with burnt areas (P = 0.005) and a positive relationship with elevation (P = 0.016). None of the assessed physiographic, edaphic, and anthropogenic variables could explain the overall abundance of K. gigas seedlings and saplings. The average above-ground carbon stored by K. gigas in Litipo forest was 3.19 ± 0.72 t ha−1, while in Mitundumbea it was 12.76 ± 1.75 t ha−1. To increase the population size and restore this once-extinct tree species, anthropogenic fires must be controlled for plant diversity conservation and environmental sustainability

Plant communities and tree species associations in a Miombo ecosystem in the Lake Rukwa basin, Southern Tanzania: implications for conservation

This study assessed the plant communities and species associations in the eastern Miombo woodlands eco-region of the Lake Rukwa basin southern Tanzania. Information was collected from 288 temporary sample plots in 32 sampling sites established randomly in the area and covering as much variation in the landscape as possible. Detailed analysis of the vegetation identified six tree communities of conservation importance, which included Brachystegia boehmii-Pericopsis angolensis woodland, Julbernardia globiflora woodland, Combretum molle-Sclerocarya birrea-Combretum zeyherii-Acacia seyal var fistula woodland, Bridelia cathartica-Diospyros mespiliformis woodland, Brachystegia bussei- Pterocarpus tinctorius woodland and Brachystegia microphylla-Isoberlinia tomentosa-Hymenocardia acida- Syzygium owariense woodland. Majority of the described plant communities are typical of Miombo ecosystems dominated by trees belonging mainly to the genera Brachystegia and Julbernardia. A mixture of non-legume species but typical of the Miombo ecosystem, however, dominates two out of six described plant communities. Apparently, there is high variability of plant communities in the Miombo ecosystem of southern Tanzania, an indication of the diverse nature of the Miombo ecosystem, also, an implication of high species diversity. This documentation on the patterns of species assemblages is the beginning of unveiling the diversity of assemblage of species in dry forest ecosystems which occupy a wide area in the region. These associations are important targets for conservation and monitoring vegetation changes in this ecosystem

Plant communities and tree species associations in a Miombo ecosystem in the Lake Rukwa basin, Southern Tanzania: implications for conservation

This study assessed the plant communities and species associations in the eastern Miombo woodlands eco-region of the Lake Rukwa basin southern Tanzania. Information was collected from 288 temporary sample plots in 32 sampling sites established randomly in the area and covering as much variation in the landscape as possible. Detailed analysis of the vegetation identified six tree communities of conservation importance, which included Brachystegia boehmii-Pericopsis angolensis woodland, Julbernardia globiflora woodland, Combretum molle-Sclerocarya birrea-Combretum zeyherii-Acacia seyal var fistula woodland, Bridelia cathartica-Diospyros mespiliformis woodland, Brachystegia bussei- Pterocarpus tinctorius woodland and Brachystegia microphylla-Isoberlinia tomentosa-Hymenocardia acida- Syzygium owariense woodland. Majority of the described plant communities are typical of Miombo ecosystems dominated by trees belonging mainly to the genera Brachystegia and Julbernardia. A mixture of non-legume species but typical of the Miombo ecosystem, however, dominates two out of six described plant communities. Apparently, there is high variability of plant communities in the Miombo ecosystem of southern Tanzania, an indication of the diverse nature of the Miombo ecosystem, also, an implication of high species diversity. This documentation on the patterns of species assemblages is the beginning of unveiling the diversity of assemblage of species in dry forest ecosystems which occupy a wide area in the region. These associations are important targets for conservation and monitoring vegetation changes in this ecosystem

Relationships between tree species richness, evenness and aboveground carbon storage in montane forests and miombo woodlands of Tanzania

Understanding how carbon storage and tree diversity are related in forests and woodlands is crucial for a sustainable flow of ecosystem goods and services. The goal of this study was to determine how tree species richness, evenness and environmental factors influence aboveground live tree carbon stocks (AGC) in two tropical vegetation types in Tanzania. We surveyed trees and sampled soil from 222 vegetation plots (20 m × 40 m) in montane forests (n = 60) and miombo woodlands (n = 162). We used a multimodel inference approach to determine how AGC related to tree species richness, evenness and environmental factors, and linear mixed effect models to test the role of tree sizes on the AGC-richness and evenness associations. AGC were related unimodally to tree species richness and evenness in the montane forest. Likewise, AGC in the miombo woodlands was positively related to tree species richness. AGC from small trees were related unimodally to tree species richness in both vegetation types. Apparently the AGC had both monotonically increasing and decreasing associations with all abiotic environmental factors in both vegetation types. We emphasize that both tree size, number of multi-stemed trees and environmental factors have an important role in determining how AGC are related to richness and evenness. Finally, management of montane forests and miombo woodlands of Tanzania to enhance ecosystem benefit, such as AGC, will require strategies that consider tree sizes, tree species richness, evenness and underlying environmental and disturbance factors

Carbon stocks of Hanang forest, Tanzania: An implication for climate mitigation

Journal ArticleThe study assessed carbon stocks of Hanang mountain forest, Tanzania. Thirty-four sample plots (40 × 50 m) were established along an altitudinal gradient. All trees with diameter at breast height ≥10 cm were identified and measured, and herb species and soil were sampled from four 1 × 1 m quadrats -1 within 10 × 10 m subplots. Mean carbon stock was 48.37 and 0.26 t C ha for tree and herb species, -1 respectively. Soil organic carbon (SOC) was 64.2, 41.93 and 31.0 t C ha in the upper, mid and lower layers, respectively. It was found that there was significant difference in tree carbon (p<0.05) along an altitudinal gradient. However there was no significant difference (p>0.05) in herbaceous carbon and SOC in the three layers along an altitudinal gradient. Tree carbon was low compared to other tropical areas where allometric models were employed. In contrast, SOC was high compared to other similar forests in the tropics. Anthropogenic threats will likely diminish the SOC hence conservation measures are needed

Relationships between tree species richness, evenness and aboveground carbon storage in montane forests and miombo woodlands of Tanzania

Understanding how carbon storage and tree diversity are related in forests and woodlands is crucial for a sustainable flow of ecosystem goods and services. The goal of this study was to determine how tree species richness, evenness and environmental factors influence aboveground live tree carbon stocks (AGC) in two tropical vegetation types in Tanzania. We surveyed trees and sampled soil from 222 vegetation plots (20 m × 40 m) in montane forests (n = 60) and miombo woodlands (n = 162). We used a multimodel inference approach to determine how AGC related to tree species richness, evenness and environmental factors, and linear mixed effect models to test the role of tree sizes on the AGC-richness and evenness associations. AGC were related unimodally to tree species richness and evenness in the montane forest. Likewise, AGC in the miombo woodlands was positively related to tree species richness. AGC from small trees were related unimodally to tree species richness in both vegetation types. Apparently the AGC had both monotonically increasing and decreasing associations with all abiotic environmental factors in both vegetation types. We emphasize that both tree size, number of multi-stemed trees and environmental factors have an important role in determining how AGC are related to richness and evenness. Finally, management of montane forests and miombo woodlands of Tanzania to enhance ecosystem benefit, such as AGC, will require strategies that consider tree sizes, tree species richness, evenness and underlying environmental and disturbance factors