Biomass estimation and carbon storage in Mangrove forests of Tanzania

This study aimed to develop tools for biomass estimation and quantify carbon stored in mangrove forests of Tanzania mainland. The study was carried out in four sites along the Tanzanian coastline; Pangani, Bagamoyo, Rufiji and Lindi-Mtwara. A total of 120 plots were measured along transects running perpendicular to sea/rivers. From each plot, one tree was destructively sampled for aboveground biomass. Thirty among 120 trees were sampled for belowground biomass. Data analysis was carried out in R software. Procedures for quantification of belowground biomass for Avicennia marina (Forssk.) Vierh, Sonneratia alba J. Smith and Rhizophora mucronata Lam. were documented in detail. Root sampling is recommended for A. marina and S. alba while for R. mucronata, total root excavation method may be applied. The methods are more comprehensive than previously reported methods, therefore they should be applied in quantification of BGB. The study found an overall mean tree aboveground basic density of 0.60±0.00 (SE) g cm -3 , 0.54 ± 0.01 (SE) g cm -3 and 0.69 ± 0.01 (SE) g cm -3 for A. marina, S. alba and R. mucronata, respectively. Similarly, the overall mean tree belowground basic density was 0.57 ± 0.02 (SE) g cm -3 , 0.32 ± 0.01 (SE) g cm -3 and 0.53 ± 0.02 (SE) g cm -3 for A. marina, S. alba and R. mucronata, respectively. The study also showed that basic density varied between species, tree sizes and tree components. Accordingly, if properly determined and applied, basic density may be useful as a conversion factor and yield accurate biomass estimates. Otherwise they are likely to be a source of uncertainties in biomass estimation. Common (multi-species) and species-specific above- and belowground biomass models for the three mangrove species were developed.ii Species-specific models had better fit than common models. Evaluation of existing biomass models on data from this study generally showed large and significant prediction errors. Possibly this may be due to application of the models beyond data size ranges, geographical locations, and differences in forest structure and tree architecture. Species-specific models from this study are therefore recommended. The use models to unrepresented species is not recommended, where necessary however a conservativeness principle (i.e. when accuracy of estimates cannot be achieved, the risk of over- or under-estimation should be minimised) need to be applied. Using biomass models from this study and forest inventory data collected by National Forest Resources Monitoring and Assessment (NAFORMA) of Tanzania, the study quantified aboveground carbon (AGC), belowground carbon (BGC) and total carbon (TC) stored in mangrove forests of Tanzania mainland. Results showed that, AGC, BGC and TC were 33.5 ± 5.8 Mg C ha -1 (53% of TC), 30.0 ± 4.5 Mg C ha -1 (47% of TC) and 63.5 ± 8.4 Mg C ha -1 respectively. Given that, mangroves of Tanzania mainland cover approximately 158, 100 ha, a total of 10.0 millions Mg C (i.e. 37.2 millions Mg CO 2 e) is stored in mangrove forests of Tanzania. Results from this study are essential for REDD+ initiatives and provides useful input in management of mangrove forests in the country.Climate Change Impacts and Mitigation Programme (CCIAM)and the Kingdom of Norwa

Biomass estimation and carbon storage in Mangrove forests of Tanzania

This study aimed to develop tools for biomass estimation and quantify carbon stored in mangrove forests of Tanzania mainland. The study was carried out in four sites along the Tanzanian coastline; Pangani, Bagamoyo, Rufiji and Lindi-Mtwara. A total of 120 plots were measured along transects running perpendicular to sea/rivers. From each plot, one tree was destructively sampled for aboveground biomass. Thirty among 120 trees were sampled for belowground biomass. Data analysis was carried out in R software. Procedures for quantification of belowground biomass for Avicennia marina (Forssk.) Vierh, Sonneratia alba J. Smith and Rhizophora mucronata Lam. were documented in detail. Root sampling is recommended for A. marina and S. alba while for R. mucronata, total root excavation method may be applied. The methods are more comprehensive than previously reported methods, therefore they should be applied in quantification of BGB. The study found an overall mean tree aboveground basic density of 0.60±0.00 (SE) g cm -3 , 0.54 ± 0.01 (SE) g cm -3 and 0.69 ± 0.01 (SE) g cm -3 for A. marina, S. alba and R. mucronata, respectively. Similarly, the overall mean tree belowground basic density was 0.57 ± 0.02 (SE) g cm -3 , 0.32 ± 0.01 (SE) g cm -3 and 0.53 ± 0.02 (SE) g cm -3 for A. marina, S. alba and R. mucronata, respectively. The study also showed that basic density varied between species, tree sizes and tree components. Accordingly, if properly determined and applied, basic density may be useful as a conversion factor and yield accurate biomass estimates. Otherwise they are likely to be a source of uncertainties in biomass estimation. Common (multi-species) and species-specific above- and belowground biomass models for the three mangrove species were developed.ii Species-specific models had better fit than common models. Evaluation of existing biomass models on data from this study generally showed large and significant prediction errors. Possibly this may be due to application of the models beyond data size ranges, geographical locations, and differences in forest structure and tree architecture. Species-specific models from this study are therefore recommended. The use models to unrepresented species is not recommended, where necessary however a conservativeness principle (i.e. when accuracy of estimates cannot be achieved, the risk of over- or under-estimation should be minimised) need to be applied. Using biomass models from this study and forest inventory data collected by National Forest Resources Monitoring and Assessment (NAFORMA) of Tanzania, the study quantified aboveground carbon (AGC), belowground carbon (BGC) and total carbon (TC) stored in mangrove forests of Tanzania mainland. Results showed that, AGC, BGC and TC were 33.5 ± 5.8 Mg C ha -1 (53% of TC), 30.0 ± 4.5 Mg C ha -1 (47% of TC) and 63.5 ± 8.4 Mg C ha -1 respectively. Given that, mangroves of Tanzania mainland cover approximately 158, 100 ha, a total of 10.0 millions Mg C (i.e. 37.2 millions Mg CO 2 e) is stored in mangrove forests of Tanzania. Results from this study are essential for REDD+ initiatives and provides useful input in management of mangrove forests in the country.Climate Change Impacts and Mitigation Programme (CCIAM)and the Kingdom of Norwa

Carbon dynamics and sequestration by urban mangrove forests of Dar es Salaam, Tanzania

This study intended to 1) determine spatial and temporal changes of mangrove forests, 2) identify drivers of mangrove deforestation and forest degradation, 3) determine historical carbon storage, sequestration and deforestation emissions by mangrove forests, and 4) determine whether mangrove forests are a source or sink of CO2 in Dar es Salaam, Tanzania. Mangrove forests have decreased from 4,813 hectares in 1986 to 1961 hectares in 2016. The following were prominent drivers of deforestation in descending order: clearing mangrove forests for salt pans; hotel construction; settlement; and charcoal making. Tree removals for firewood and building poles were also prominent drivers of mangrove forest degradation. Similarly, carbon stored in mangrove forests has decreased from 1,131,055 tonnes CO2e in 1986 to 460,835 tonnes CO2e in 2016. Sequestration of CO2 by mangrove forests is estimated at 133,516 (1986-1995); 106,110 (1995-2006) and 69,616 (2006-2016) tonnes CO2e year-1. Conversely, mangrove deforestation has resulted in emissions of about 27,400, 16,500 and 24,000 tonnes CO2e year-1 in 1986-1995, 1995- 2006 and 2006-2016, respectively. Urban mangrove forests play an important environmental role in mitigating climate change and amelioration of local weather through the large carbon stocks they store and sequester. Mangrove forests in the study area remain a net carbon sink, however, the sink role played by mangrove forests in the study area is decreasing rapidly. The declining spatial and temporal trends of urban mangrove forest cover has resulted in a systematic decrease in the total carbon stored and sequestered by mangrove forests. In the absence of timely measures of preserving and rehabilitating degraded mangrove areas, the mangrove forests of Dar es Salaam may become the source of CO2. The study recommends effective urban land use planning and effective law enforcement to ensure a win-win situation through sustained ecosystem services offered by urban mangrove forests to support economic growth

Are miombo woodlands vital to livelihoods of rural households? Evidence from Urumwa and surrounding communities, Tabora, Tanzania

Forests, trees and livelihoods 2013; 22(2):124-140This study investigated contribution of miombo woodland resources accrued from Urumwa Forest Reserve (UFR) to income of rural households. Data and conclusions are based on 84 randomly surveyed households in four villages adjacent to UFR. Using descriptive statistics, the analysis was guided by the sustainable livelihood framework conceptual model. Results show that the miombo woodlands of the UFR account for 42% of total household income. Further analysis reveals that woodlands contribute 28% and 59% of non-monetary and monetary income, respectively. This demonstrates a significant role played by miombo woodlands. Woodland resources contribute to household income through various livelihood activities. Accordingly the woodland resources accrued from the UFR cover human basic needs. Results from this study empirically demonstrate the vital role played by miombo woodlands in either supporting current consumption or serving as safety net. It is, therefore, recommended that current and future management strategies in the forest sector emphasize forest and livelihood dimensions for sustainability of both livelihood and forest and woodland resources

Are miombo woodlands vital to livelihoods of rural households? Evidence from Urumwa and surrounding communities, Tabora, Tanzania

Forests, trees and livelihoods 2013; 22(2):124-140This study investigated contribution of miombo woodland resources accrued from Urumwa Forest Reserve (UFR) to income of rural households. Data and conclusions are based on 84 randomly surveyed households in four villages adjacent to UFR. Using descriptive statistics, the analysis was guided by the sustainable livelihood framework conceptual model. Results show that the miombo woodlands of the UFR account for 42% of total household income. Further analysis reveals that woodlands contribute 28% and 59% of non-monetary and monetary income, respectively. This demonstrates a significant role played by miombo woodlands. Woodland resources contribute to household income through various livelihood activities. Accordingly the woodland resources accrued from the UFR cover human basic needs. Results from this study empirically demonstrate the vital role played by miombo woodlands in either supporting current consumption or serving as safety net. It is, therefore, recommended that current and future management strategies in the forest sector emphasize forest and livelihood dimensions for sustainability of both livelihood and forest and woodland resources

Mixed method approaches to evaluate conservation impact: evidence from decentralized forest management in Tanzania

Nearly 10% of the world’s total forest area is formally owned by communities and indigenous groups, yet knowledge of the effects of decentralized forest management approaches on conservation (and livelihood) impacts remains elusive. In this paper, the conservation impact of decentralized forest management on two forests in Tanzania was evaluated using a mixed method approach. Current forest condition, forest increment and forest use patterns were assessed through forest inventories, and changes in forest disturbance levels before and after the implementation of decentralized forest management were assessed on the basis of analyses of Landsat images. This biophysical evidence was then linked to changes in actual management practices, assessed through records, interviews and participatory observations, to provide a measure of the conservation impact of the policy change. Both forests in the study were found to be in good condition, and extraction was lower than overall forest increment. Divergent changes in forest disturbance levels were in evidence following the implementation of decentralized forest management. The evidence from records, interviews and participatory observations indicated that decent- ralized management had led to increased control of forest use and the observed divergence in forest disturbance levels appeared to be linked to differences in the way that village-level forest managers prioritized conservation objectives and forest-based livelihood strategies. The study illustrates that a mixed methods approach comprises a valid and promising way to evaluate impacts of conservation policies, even in the absence of control sites. By carefully linking policy outcomes to policy outputs, such an approach not only identifies whether such policies work as intended, but also potential mechanisms

Mixed method approaches to evaluate conservation impact: evidence from decentralized forest management in Tanzania

Nearly 10% of the world’s total forest area is formally owned by communities and indigenous groups, yet knowledge of the effects of decentralized forest management approaches on conservation (and livelihood) impacts remains elusive. In this paper, the conservation impact of decentralized forest management on two forests in Tanzania was evaluated using a mixed method approach. Current forest condition, forest increment and forest use patterns were assessed through forest inventories, and changes in forest disturbance levels before and after the implementation of decentralized forest management were assessed on the basis of analyses of Landsat images. This biophysical evidence was then linked to changes in actual management practices, assessed through records, interviews and participatory observations, to provide a measure of the conservation impact of the policy change. Both forests in the study were found to be in good condition, and extraction was lower than overall forest increment. Divergent changes in forest disturbance levels were in evidence following the implementation of decentralized forest management. The evidence from records, interviews and participatory observations indicated that decent- ralized management had led to increased control of forest use and the observed divergence in forest disturbance levels appeared to be linked to differences in the way that village-level forest managers prioritized conservation objectives and forest-based livelihood strategies. The study illustrates that a mixed methods approach comprises a valid and promising way to evaluate impacts of conservation policies, even in the absence of control sites. By carefully linking policy outcomes to policy outputs, such an approach not only identifies whether such policies work as intended, but also potential mechanisms

Mixed method approaches to evaluate conservation impact:evidence from decentralized forest management in Tanzania

This article is available at http://www.doi.org/10.1017/S0376892914000241Nearly 10% of the world’s total forest area is formally owned by communities and indigenous groups, yet knowledge of the effects of decentralized forest management approaches on conservation (and livelihood) impacts remains elusive. In this paper, the conservation impact of decentralized forest management on two forests in Tanzania was evaluated using a mixed method approach. Current forest condition, forest increment and forest use patterns were assessed through forest inventories, and changes in forest disturbance levels before and after the implementation of decentralized forest management were assessed on the basis of analyses of Landsat images. This biophysical evidence was then linked to changes in actual management practices, assessed through records, interviews and participatory observations, to provide ameasure of the conservation impact of the policy change. Both forests in the study were found to be in good condition, and extraction was lower than overall forest increment. Divergent changes in forest disturbance levels were in evidence following the implementation of decentralized forest management. The evidence from records, interviews and participatory observations indicated that decentralized management had led to increased control of forest use and the observed divergence in forest disturbance levels appeared to be linked to differences in theway that village-level forest managers prioritized conservation objectives and forest-based livelihood strategies. The study illustrates that a mixed methods approach comprises a valid and promising way to evaluate impacts of conservation policies, even in the absence of control sites. By carefully linking policy outcomes to policy outputs, such an approach not onlyidentifies whether such policies work as intended, but also potential mechanisms