Browsing by Author "Zahabu, Eliakimu"

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Above- and belowground tree biomass models for three mangrove species in Tanzania: a nonlinear mixed effects modelling approach
(Springer, 2015-10) Njana, Marco Andrew; Bollandsås, Ole Martin; Eid, Tron; Malimbwi, Rogers Ernest; Zahabu, Eliakimu
& Key message Tested on data from Tanzania, both existing species-specific and common biomass models developed elsewhere revealed statistically significant large prediction errors. Species-specific and common above- and below- ground biomass models for three mangrove species were therefore developed. The species-specific models fitted bet- ter to data than the common models. The former models are recommended for accurate estimation of biomass stored in mangrove forests of Tanzania. & Context Mangroves are essential for climate change mitiga- tion through carbon storage and sequestration. Biomass models are important tools for quantifying biomass and car- bon stock. While numerous aboveground biomass models exist, very few studies have focused on belowground biomass, and among these, mangroves of Africa are hardly or not represented.
Allometric models for estimating tree volume and aboveground biomass in lowland forests of Tanzania
(International Journal of Forestry Research, 2016) Mugasha, Wilson Ancelm; Mwakalukwa, Ezekiel Edward; Luoga, Emannuel; Malimbwi, Rogers Ernest; Zahabu, Eliakimu; Silayo, Dos Santos; Sola, Gael; Crete, Philippe; Henry, Matieu; Kashindye, Almas
Models to assist management of lowland forests in Tanzania are in most cases lacking. Using a sample of 60 trees which were destructively harvested from both dry and wet lowland forests of Dindili in Morogoro Region (30 trees) and Rondo in Lindi Region (30 trees), respectively, this study developed site specific and general models for estimating total tree volume and aboveground biomass. Specifically the study developed (i) height-diameter (ht-dbh) models for trees found in the two sites, (ii) total, merchantable, and branches volume models, and (iii) total and sectional aboveground biomass models of trees found in the two study sites. The findings show that site specific ht-dbh model appears to be suitable in estimating tree height since the tree allometry was found to differ significantly between studied forests. The developed general volume models yielded unbiased mean prediction error and hence can adequately be applied to estimate tree volume in dry and wet lowland forests in Tanzania. General aboveground biomass model appears to yield biased estimates; hence, it is not suitable when accurate results are required. In this case, site specific biomass allometric models are recommended. Biomass allometric models which include basic wood density are highly recommended for improved estimates accuracy when such information is available.
At the heart of REDD+: a role for local people in monitoring forests?
(Wiley Periodicals, Inc., 2011) Danielsen, Finn; Skutsch, Margaret; Burgess, Neil D; Jensen, Per Moestrup; Andrianandrasana, Herizo; Karky, Bhaskar; Lewis, Richard; Lovett, Jon C; Ngaga, Yonika; Phartiyal, Pushkin; Poulsen, Michael Køie; Singh, S. P; Solis, Silvia; Sørensen, Marten; Tewari, Ashish; Young, Richard; Zahabu, Eliakimu
Reduced Emissions from Deforestation and Forest Degradation in Developing Countries (REDD+) is a policy mechanism now agreed under the United Na- tions Framework Convention on Climate Change (UNFCCC). It aims to reduce carbon dioxide emissions from developing countries through the sustainable management of forests, while providing co-benefits of biodiversity conserva- tion and livelihood support. Implementation challenges include linking remote sensing and national forest inventories of carbon stocks, to local implementa- tion and measuring carbon loss from forest degradation. Community-based forest monitoring can help overcome some of these challenges. We show that local people can collect forest condition data of comparable quality to trained scientists, at half the cost. We draw on our experience to propose how and where local REDD+ monitoring can be established. Empowering communities to own and monitor carbon stocks could provide a rapid and cost-effective way of absorbing carbon dioxide emissions, while potentially contributing to local livelihoods and forest biodiversity conservation.
Carbon stocks for different land cover types in Mainland Tanzania
(2019-04) Malimbwi, Rogers; Zahabu, Eliakimu; Njana, Marco Andrew; Mugasha, Wilson Ancelm; Mauya, Ernest William
Background: Developing countries participating in the mitigation mechanism of reducing emissions from defor- estation and forest degradation (REDD+), are required to establish a forest reference emission level (FREL), if they wish to seek financial support to reduce carbon emissions from deforestation and forest degradation. However, establish- ment of FREL relies heavily on the accurate estimates of carbon stock as one of the input variable for computation of the emission factors (EFs). The product of an EF and activity data, such as the area of deforestation, results in the total emissions needed for establishment of FREL. This study presents the carbon stock estimates for different land cover classes based on an analysis of Tanzania’s national forest inventory data generated through the National Forest Resources Monitoring and Assessment (NAFORMA). Results: Carbon stocks were estimated in three carbon pools, namely aboveground, belowground, and deadwood for each of the three land cover classes (i.e. Forest, non-forest, and wetland). The weighted average carbon stock was 33.35 t C ha −1 for forest land, 4.28 t ha −1 for wetland and 5.81 t ha −1 for non-forest land. The uncertainty values were 0.9% for forest land, 11.3% for wetland and 1.8% for non-forest land. Average carbon stocks for land cover sub-classes, which make up the above mentioned major land cover classes, are also presented in our study. Conclusions: The values presented in this paper correspond to IPCC tier 3 and can be used for carbon estimation at the national scale for the respective major primary vegetation type for various purposes including REDD+. However, if local based estimates values are needed, the use of auxiliary data to enhance the precision of the area of interest is recommended. Keywords: Carbon stock, REDD+, FREL, Emission factor, Uncertainty
Deforestation and connectivity among protected areas of Tanzania
(MDPI, 2020-02-04) Gizachew, Belachew; Rizzi, Jonathan; Shirima, Deo D; Zahabu, Eliakimu
Protected Areas (PAs) in Tanzania had been established originally for the goal of habitat, landscape and biodiversity conservation. However, human activities such as agricultural expansion and wood harvesting pose challenges to the conservation objectives. We monitored a decade of deforestation within 708 PAs and their unprotected buffer areas, analyzed deforestation by PA management regimes, and assessed connectivity among PAs. Data came from a Landsat based wall-to-wall forest to non-forest change map for the period 2002–2013, developed for the definition of Tanzania’s National Forest Reference Emissions Level (FREL). Deforestation data were extracted in a series of concentric bands that allow pairwise comparison and correlation analysis between the inside of PAs and the external buffer areas. Half of the PAs exhibit either no deforestation or significantly less deforestation than the unprotected buffer areas. A small proportion (10%; n = 71) are responsible for more than 90% of the total deforestation; but these few PAs represent more than 75% of the total area under protection. While about half of the PAs are connected to one or more other PAs, the remaining half, most of which are Forest Reserves, are isolated. Furthermore, deforestation inside isolated PAs is significantly correlated with deforestation in the unprotected buffer areas, suggesting pressure from land use outside PAs. Management regimes varied in reducing deforestation inside PA territories, but differences in protection status within a management regime are also large. Deforestation as percentages of land area and forested areas of PAs was largest for Forest Reserves and Game Controlled areas, while most National Parks, Nature Reserves and Forest Plantations generally retained large proportions of their forest cover. Areas of immediate management concern include the few PAs with a disproportionately large contribution to the total deforestation, and the sizeable number of PAs being isolated. Future protection should account for landscapes outside protected areas, engage local communities and establish new PAs or corridors such as village-managed forest areas.
Effect of spacing regimes on growth, yield, and wood properties of tectona grandis at Longuza forest plantation, Tanzania
(International Journal of Forestry Research, 2015) Zahabu, Eliakimu; Raphael, Tumaini; Chamshama, Shabani Athumani Omari; Iddi, Said; Malimbwi, Rogers Ernest
This study examined the effects of planting spacing on growth, yield, and wood properties of teak planted at square spacing regimes of 2 m, 3 m, and 4 m at Longuza Forest Plantation, Tanzania. To achieve this, tree, stand, and wood properties were studied at age of 14 years. Results showed that diameter at breast height and total height increased with increasing spacing. Mean annual increment increased significantly with increasing spacing while spacing did not have significant effect on total volume production and basal area. Basic density is also not affected by spacing while heartwood proportion increases as planting spacing increases. All studied wood properties (modulus of rupture, modulus of elasticity, compression strength tangential to grain, and shear tangential to the grain) except cleavage tangential to grain were not significantly affected by increasing spacing. It is recommended to use the spacing of 3 × 3 m, but if thinning can be done before onset of competition at 5 years, the currently used spacing of 2.5 × 2.5 m can still be used. However, the use of a spacing of 4 × 4 m can give at least 50% heartwood at shorter rotation age of 30 years.
Forestland tenure systems in Tanzania: an overview of policy changes in relation to forest management
(Department of Ecology and Natural Resource Management Norwegian University of Life Sciences, 2009) Zahabu, Eliakimu; Eid, Tron; Kajembe, George; Mbwambo, L.; Mongo, Cellina; Sangeda, Anthony; Malimbwi, Rogers; Katan, Josiah; Kashaigili, Japhet; Luoga, Emmanuel
ummary Zahabu, E., Eid, T., Kajembe, G. C., Mbwambo, L., Mongo, C., Sangeda, A.Z., Malimbwi, R. E., Katani, J.Z., Kashaigili, J.J. and Luoga, E.J. 2009. Forestland tenure systems in Tanzania: an overview of policy changes in relation to forest management [Eiendomsforholdene for skogarealer i Tanzania: en oversikt over policyendringer i skogforvaltningen]. INA-fagrapport no. 14, 24 pp. A review of the role of forestland tenure systems in Tanzania, and how different forestland tenure approaches and reforms have influenced forest management is presented. The complexity of land reforms and processes that have taken place in Tanzania during the pre-colonial, colonial and post-independence periods is discussed. The pre-colonial period, though not much is written, was characterised by forest management through traditional institutions, low population and low forest resources exploitation. Colonial governments undermined the role of local traditions in managing the forests related to for example burial areas and springs. They also established forest reserves and in some areas cleared indigenous forests to establish tea, coffee and exotic fruit and timber plantations. Different land reforms that were geared towards sustainable development occurred after independence, forests depletion continued, however. Currently, it is observed that there coexists state, village, private and collective rights on forests without clear ownership. This is greatly linked to the ongoing deforestation and forest degradation in the country. In this situation, sustainable forestland use may be attained through establishing an enabling environment that allows effective local communities’ participation in forest management. Sustainable management, however, always presupposes effective control of harvesting and other activities to secure the carrying capacity of forests and woodlands, whether it is undertaken by central authorities or local people. Studies on forestland tenures and rights, and the impact of changes in tenures and rights on forest resources and rural livelihoods are therefore important. Such studies are required for the provision of facts for the establishment of proper future policy means that aim at reducing forest degradation and improving livelihoods in Tanzania.
Forestland tenure systems in Tanzania: an overview of policy changes in relation to forest management
(INA fagrapport, 2009) Zahabu, Eliakimu; Eid, Tron; Kajembe, George; Mbwambo, Lawrence; Mongo, Cellina; Sangeda, Anthony; Malimbwi, Rogers; Katani, Josiah; Kashaigili, Japhet; Luoga, Emmanuel
A review of the role of forestland tenure systems in Tanzania, and how different forestland tenure approaches and reforms have influenced forest management is presented. The complexity of land reforms and processes that have taken place in Tanzania during the pre-colonial, colonial and post-independence periods is discussed. The pre-colonial period, though not much is written, was characterised by forest management through traditional institutions, low population and low forest resources exploitation. Colonial governments undermined the role of local traditions in managing the forests related to for example burial areas and springs. They also established forest reserves and in some areas cleared indigenous forests to establish tea, coffee and exotic fruit and timber plantations. Different land reforms that were geared towards sustainable development occurred after independence, forests depletion continued, however. Currently, it is observed that there coexists state, village, private and collective rights on forests without clear ownership. This is greatly linked to the ongoing deforestation and forest degradation in the country. In this situation, sustainable forestland use may be attained through establishing an enabling environment that allows effective local communities’ participation in forest management. Sustainable management, however, always presupposes effective control of harvesting and other activities to secure the carrying capacity of forests and woodlands, whether it is undertaken by central authorities or local people. Studies on forestland tenures and rights, and the impact of changes in tenures and rights on forest resources and rural livelihoods are therefore important. Such studies are required for the provision of facts for the establishment of proper future policy means that aim at reducing forest degradation and improving livelihoods in Tanzania.
Impact of charcoal extraction on the miombo woodlands: The case of Kitulangalo area, Tanzania
(Sokoine University of Agriculture, 2001) Zahabu, Eliakimu
1‘liis study was carried out to determine the impact of charcoal extraction to the miombo woodlands of Kitulangalo area, near Morogoro. Tanzania. Both socio economic and ecological aspects of charcoal production were studied. While the socio-economic study involved interviewing 50% of charcoal makers in two villages of Gwata-Ujembc and Mascyu. ecological survey was done in Kitulangalo SUA Training Forest Reserve and the adjacent public lands. Systematic sampling design used in an inventory in 1996 was repeated in 1999 in order to determine current stand parameters and the forest change in general, including mean annual volume increment. A total of 46 sample plots were laid out in the forest reserve. In public lands stratified random sampling was applied where a total of 30 plots were laid at an interval of 500 m apart on three and two transects laid perpendicular to the access road and highway respectively at 0 km. 5 km. 10 km and 15 km interval. An average charcoal making household was found to produce 43 bags of charcoal per month. sold at Tshs. 1.000/= (USD 1.25 . 1 USD = Tshs. 800/- in 1999) per bag. The household realizes an income of Tshs. 43.000/= per month which is above the minimum salary rates paid currently to government workers and hence attracts more people to join the business. The kiln efficiencies were observed to range from 17.5% to about 30%. There is therefore a need to explore desirable ways of kiln preparation and carbonization that can improve kiln efficiencies right at the field and not from modern technologies which in most cases are expensive. The mean charcoal kiln efficiency was found to be 23%. Preferred tree species for charcoal making include: Jidhernadia globiflora. Hrachyxteyia boehmii. Tamarindux indica. Acacia nigrexcex. .■I. yerrardii. .1. ndolica. .1. yoetzei xubxp yoelzei. Combretum adenoyonium. C. moHe. C. zeyheri. ('. codinum. IJoxcia xaPtcifolia. Diplorhynchux condylocarpon. Pxeudolachnoxtylix maproiineifolia. Terminalia Dioxpyrox kirkii. Xeroderrix xtuhlmannii. mollix. Pteleopxix myrtifolia. Mimuxopx kummeL Albizia harvey. Lonchocarpux capaxxa and Lannen xchimperi. These species were having standing wood volume of 24.5 nr’ha’1 and 56.5 m’ha'1 in public lands and reserved forest respectively with corresponding basal area of 3.7 irrha’1 and 7.2 irrha’1 suggesting low biomass in public lands compared to reserved forest. Stem numbers were 909 stems ha’1 in public lands and 354 stems ha’1 in forest reserve showing a reversed trend compared to basal area and volume. This indicates more regeneration in public land following disturbance than in the forest reserve. The public lands at roadside are dominated by large trees of Acacia polyacantha. a pioneer tree species which is not preferred for charcoal making due to its hooked thorns and lighter charcoal which breaks easily during transportation. Other un-preferred tree species for charcoal making were Sterculia africana and Adanxonia digitata due to their low density charcoal. The Important Value Index (IVI). indicated that J. globijlora is the most important tree species in both public lands and reserved forest. The species is among the suitable tree species for charcoal making. The Index of Dominance (ID) was 0.092 and 0.065 in public lands and reserved forest respectively, indicating high species richness in forest reserve compared to the public lands. The Shannon-Wiener Index of Divers ity (H) calculated using natural logarithms were 2.9 and 3.13 in public land and reserved forest respectively, also suggesting high species diversity in forest reserve compared to the public lands. Considering a conversion factor of fresh wood volume to wood biomass of 0.85 and kiln efficiency of 23%. the weight of charcoal that can be extracted from the woodland at the roadside is 56 kgs of charcoal, equivalent to only one bag of charcoal per hectare. Similarly 54 bags may be expected al 5 km distance while 125 bags may be extracted from beyond 10 km from the highway. With the established stand growth rate of 2.3 in ’ha‘lyear’1 for the re-growth miombo woodland al Kilulangalo. charcoal production could be sustained al the levels observed at beyond 10 km away from the highway within felling cycles range of 8 to 15 years for degraded forest at 5 km away from the highway and at roadside.
The likely mechanism for implementing REDD policy in Tanzania
(Think Global Act Local, Research Project, 2012) Zahabu, Eliakimu; Skutsch, Margaret; Malimbwi, Rogers. E.; Nordholt, N.G. Schulte
Till 2012, establishing new forest is the only eligible practice for forest carbon trading under the Clean Development Mechanism (CDM) of the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC). Management of natural forest is not credited at present. Reduced Emissions from Deforestation and forest Degradation (REDD) policy, is an alternative mechanism that is still discussed for the post 2012 regime. Under REDD, countries would, on a voluntary basis, aim to reduce the rate at which their forests are being lost, and receive compensation in proportion to the carbon emissions saved compared to a baseline reference scenario which represent the ‘without intervention’ case. The REDD policy is therefore likely to be undertaken nationally, the country deforestation baseline would be determined by depicting historical land use changes from satellite imagery and typical carbon stock data for different types of forests to calculate the changes in terms of tons of carbon. After developing national level reference scenarios for the entire country, a system of ‘nested baselines’ i.e. an interlocking set of baselines that covers the whole country and sums to the national baseline is needed. ‘Nested baselines’ are necessary to operationalize REDD internally for the different geographic regions and to account for different forest regimes e.g. national parks, forest reserves, community forests, and private forests. This system is needed in order to provide incentives to stakeholders who are responsible for reductions in carbon losses within the country. In line with the current forest policy, the government is urged to consider Participatory Forest Management (PFM) as part of their approach under REDD. The established village framework in the Tanzanian Government offers the opportunity for implementing the REDD policy nationally. This can be achieved through developing and implementing land use plan for each village. From the start of the project, monitoring is done to determine the standing stock in both protective forests and productive forests. For a village to be rewarded carbon credits at any accounting time there must be evidence of forest enhancement or reduced deforestation/degradation. Since there are no data on carbon stocks, studies on forest inventories using methodology such as that developed by the Kyoto: Think Global Act Local research project are recommended. Possible strategy for the scaling up of the participatory inventory methodology is to train villagers and their local supporting forest staff to carry-out forest inventories on their own in the entire country.
Mapping and estimating the total living biomass and carbon in low‐biomass woodlands using landsat 8 CDR data
(CrossMark, 2016-06-24) Gizachew, Belachew; Solberg, Svein; Næsset, Erik; Gobakken, Terje; Bollandsås, Ole Martin; Breidenbach, Johannes; Zahabu, Eliakimu; Mauya, Ernest William
Background: A functional forest carbon measuring, reporting and verification (MRV) system to support climate change mitigation policies, such as REDD+, requires estimates of forest biomass carbon, as an input to estimate emis- sions. A combination of field inventory and remote sensing is expected to provide those data. By linking Landsat 8 and forest inventory data, we (1) developed linear mixed effects models for total living biomass (TLB) estimation as a function of spectral variables, (2) developed a 30 m resolution map of the total living carbon (TLC), and (3) estimated the total TLB stock of the study area. Inventory data consisted of tree measurements from 500 plots in 63 clusters in a 15,700 km 2 study area, in miombo woodlands of Tanzania. The Landsat 8 data comprised two climate data record images covering the inventory area. Results: We found a linear relationship between TLB and Landsat 8 derived spectral variables, and there was no clear evidence of spectral data saturation at higher biomass values. The root-mean-square error of the values predicted by the linear model linking the TLB and the normalized difference vegetation index (NDVI) is equal to 44 t/ha (49 % of the mean value). The estimated TLB for the study area was 140 Mt, with a mean TLB density of 81 t/ha, and a 95 % confidence interval of 74–88 t/ha. We mapped the distribution of TLC of the study area using the TLB model, where TLC was estimated at 47 % of TLB. Conclusion: The low biomass in the miombo woodlands, and the absence of a spectral data saturation problem sug- gested that Landsat 8 derived NDVI is suitable auxiliary information for carbon monitoring in the context of REDD+, for low-biomass, open-canopy woodlands.
Modeling aboveground biomass in dense tropical submontane rainforest using airborne laser scanner data
(MDPI [Commercial Publisher], 2015-01-14) Hansen, Endre Hofstad; Gobakken, Terje; Bollandsås, Ole Martin; Zahabu, Eliakimu; Næsset, Erik
Successful implementation of projects under the REDD+ mechanism, securing payment for storing forest carbon as an ecosystem service, requires quantification of biomass. Airborne laser scanning (ALS) is a relevant technology to enhance estimates of biomass in tropical forests. We present the analysis and results of modeling aboveground biomass (AGB) in a Tanzanian rainforest utilizing data from a small-footprint ALS system and 153 field plots with an area of 0.06–0.12 ha located on a systematic grid. The study area is dominated by steep terrain, a heterogeneous forest structure and large variation in AGB densities with values ranging from 43 to 1147 Mg·ha −1 , which goes beyond the range that has been reported in existing literature on biomass modeling with ALS data in the tropics. Root mean square errors from a 10-fold cross-validation of estimated values were about 33% of a mean value of 462 Mg·ha −1 . Texture variables derived from a canopy surface model did not result in improved models. Analyses showed that (1) variables derived from echoes in the lower parts of the canopy and (2) canopy density variables explained more of the AGB density than variables representing the height of the canopy.
Modelling aboveground forest biomass using airborne laser scanner data in the miombo woodlands of Tanzania
(Springer, 2015) Mauya, Ernest William; Ene, Liviu Theodor; Bollandsås, Ole Martin; Gobakken, Terje; Næsset, Erik; Malimbwi, Rogers Ernest; Zahabu, Eliakimu
Background: Airborne laser scanning (ALS) has emerged as one of the most promising remote sensing technologies for estimating aboveground biomass (AGB) in forests. Use of ALS data in area-based forest inventories relies on the development of statistical models that relate AGB and metrics derived from ALS. Such models are firstly calibrated on a sample of corresponding field- and ALS observations, and then used to predict AGB over the entire area covered by ALS data. Several statistical methods, both parametric and non-parametric, have been applied in ALS-based forest inventories, but studies that compare different methods in tropical forests in particular are few in number and less fre- quent than studies reported in temperate and boreal forests. We compared parametric and non-parametric methods, specifically linear mixed effects model (LMM) and k-nearest neighbor (k-NN). Results: The results showed that the prediction accuracy obtained when using LMM was slightly better than when using the k-NN approach. Relative root mean square errors from the cross validation was 46.8 % for the LMM and 58.1 % for the k-NN. Post-stratification according to vegetation types improved the prediction accuracy of LMM more as compared to post-stratification by using land use types. Conclusion: Although there were differences in prediction accuracy between the two methods, their accuracies indicated that both of methods have potentials to be used for estimation of AGB using ALS data in the miombo woodlands. Future studies on effects of field plot size and the errors due to allometric models on the prediction accu- racy are recommended. Keywords: Parametric models, Prediction accuracy, Non-parametric models, LMM, k-NN, Sampling design
Models for estimation of tree volume in the miombo woodlands of Tanzania
(Southern Forests: a Journal of Forest Science, 2014) Mauya, Ernest W.; Mugasha, Wilson A.; Zahabu, Eliakimu; Bollandsås, Ole M.; Eid, Tron
Volume of trees is an important parameter in forest management, but only volume models with limited geographical and tree size coverage have previously been developed for Tanzanian miombo woodlands. This study developed models for estimating total, merchantable stem and branches volume applicable for the entire miombo woodlands of Tanzania. We used data from 158 destructively sampled trees, including 55 tree species collected from wide geographical and biophysical ranges. We developed general and site-specific models with diameter at breast height only as the independent variable, together with models with both diameter at breast height and tree height. Leave-one-out cross-validation was used to evaluate the models. The total tree volume models that included diameter at breast height and tree height had appropriate predictive capabilities with relative root mean square errors (RMSEr) ranging from 30.5% to 47.6%. The RMSEr for total tree volume models with diameter at breast height only ranged from 39.9% to 48.0%. The site-specific models had slightly lower RMSEr values relative to the general models. The relative mean prediction error of the general total tree volume model with diameter at breast height and tree height was lower (0.6%) than those of the previously developed models (−30.7% to 31.2%). Based on the evaluations, we recommend the general total tree models to be applied over a wide range of geographical and biophysical conditions in Tanzania.
Monitoring forest carbon in a Tanzanian woodland using interferometric SAR: a novel methodology for REDD+
(Springer, 2015) Solberg, Svein; Gizachew, Belachew; Næsset, Erik; Gobakken, Terje; Bollandsås, Ole Martin; Mauya, Ernest William; Olsson, Håkan; Malimbwi, Rogers; Zahabu, Eliakimu
Background: REDD+ implementation requires establishment of a system for measuring, reporting and verification (MRV) of forest carbon changes. A challenge for MRV is the lack of satellite based methods that can track not only deforestation, but also degradation and forest growth, as well as a lack of historical data that can serve as a basis for a reference emission level. Working in a miombo woodland in Tanzania, we here aim at demonstrating a novel 3D satellite approach based on interferometric processing of radar imagery (InSAR). Results: Forest carbon changes are derived from changes in the forest canopy height obtained from InSAR, i.e. decreases represent carbon loss from logging and increases represent carbon sequestration through forest growth. We fitted a model of above-ground biomass (AGB) against InSAR height, and used this to convert height changes to biomass and carbon changes. The relationship between AGB and InSAR height was weak, as the individual plots were widely scattered around the model fit. However, we consider the approach to be unique and feasible for large-scale MRV efforts in REDD+ because the low accuracy was attributable partly to small plots and other limitations in the data set, and partly to a random pixel-to-pixel variation in trunk forms. Further processing of the InSAR data provides data on the categories of forest change. The combination of InSAR data from the Shuttle RADAR Topography Mission (SRTM) and the TanDEM-X satellite mission provided both historic baseline of change for the period 2000–2011, as well as annual change 2011–2012. Conclusions: A 3D data set from InSAR is a promising tool for MRV in REDD+. The temporal changes seen by InSAR data corresponded well with, but largely supplemented, the changes derived from Landsat data.
NAFORMA: National forest resources monitoring and assessment of Tanzania Mainland
(FAO, 2022) Rajala, Tuomas; Heikkinen, Juha; Gogo, Sophia; Ahimbisibwe, Joyce; Bakanga, Geofrey; Chamuya, Nurdin; Perez, Javier Garcia; Kilawe, Edward; Kiluvia, Shani; Morales, David; Nzunda, Emmanuel; Otieno, Jared; Sawaya, Jonathan; Vesa, Lauri; Zahabu, Eliakimu; Henry, Matieu
hree options for the sampling design of the field plot clusters of NAFORMA II biophysical survey are compared in this report. Option 1 consists of re-measuring all NAFORMA I field sample plots (3 205 clusters) and Option 2 of re-measuring only those that were established as permanent (848 clusters). The recommended Option 3 is a compromise between these two “extreme” options: Re-measure a subset (1 405 clusters) of NAFORMA I field sample plots including (almost) all permanent clusters and a carefully selected set of other NAFORMA I field plot clusters to obtain a uniform sample within each TFS zone. Design Option 3 has the following features: • • • • Sampling intensity is uniform within each TFS zone. This makes it simple to use the data. For example, mean volumes can be estimated by averages over the plots. The selected clusters are well-spread over the target population. The anticipated precision of land-class area and mean wood volume relative to sample size is nearly as good as that of NAFORMA I. All proposed clusters were measured in NAFORMA I, which enables precise estimation of change based on repeated measurements. The costs and precision were anticipated by utilizing NAFORMA I field data, information about subsequent improvements in the road network, and changes in land-use using satellite imaging derived land-class maps.
Procedures for quantification of belowground biomass of three mangrove tree species
(Springer Science, 2015-02) Njana, Marco Andrew; Eid, Tron; Zahabu, Eliakimu; Malimbwi, Rogers
A review of studies on belowground biomass (BGB) of mangroves revealed that proce- dures for excavation and determination of dry weight are insufficiently documented. The main objective of this study was therefore to describe procedures for quantification of tree BGB for Avicennia marina (Forssk.), Sonneratia alba J. Smith and Rhizophora mucronata Lam. The study covered four sites in Tanzania where 30 trees were sampled (10 for each species). A new root sampling procedure applied for A. marina and S. alba seemed to work adequately. Dry to fresh weight ratios (DF-ratios) varied between tree species, between tree sizes and between root compo- nents. Therefore, for each tree species, tree- and root component-specific DF-ratios were applied for dry weight determination. For A. marina and S. alba trees, a significant proportion of total tree BGB is stored in the root crown (34 and 10 % respectively). Future studies should therefore ensure inclusion of root crown when accounting for total tree BGB.
Reduced emissions from deforestation and degradation
(Blackwell Publishing Ltd, Afr., 2007) Zahabu, Eliakimu; Skutsch, Margaret M.; Sosovele, Hussein; Malimbwi, Rogers E.
Introduction Until now forest carbon trading has been possible only through the Clean Development Mechanism (CDM) of the Kyoto Protocol of the United Nations Framework Con- vention on Climate Change (UNFCCC). But CDM is limited to afforestation and reforestation projects. The option for reducing rates of carbon emissions by improved forest management and by avoided deforestation is not eligible, despite the fact that the Intergovernmental Panel on Cli- mate Change (IPCC) estimates that 20–25% of current annual carbon emissions result from loss of tropical forest (IPCC, 2007). The contribution of tropical deforestation to global carbon emissions has prompted re-negotiation of climate change policy to include Reduced Emissions from Deforestation and Degradation (REDD). This would allow tropical forest nations to claim for compensation, if they reduce national rates of deforestation and degradation through management of natural forests
A sampling design for a large area forest inventory: case Tanzania
(NRC Research Press, 2014-04-21) Tomppo, Erkki; Malimbwi, Rogers; Katila, Matti; Mäkisara, Kai; Chamuya, Nurdin; Zahabu, Eliakimu; Otieno, Jared; Henttonen, Helena M.
Methods for constructing a sampling design for large area forest inventories are presented. The methods, data sets used, and the procedures are demonstrated in a real setting: constructing a sampling design for the first national forest inventory for Tanzania. The approach of the paper constructs a spatial model of forests, landscape, and land use. Sampling errors of the key parameters as well as the field measurement costs of the inventory were estimated using sampling simulation on data. Forests and land use often vary within a country or an area of interest, implying that stratified sampling is an efficient inventory design. Double sampling for stratification was taken for the statistical framework. The work was motivated by the approach used by The Food and Agriculture Organization of the United Nations (FAO) in supporting nations to establish forest inventories. The approach taken deviates significantly from the traditional FAO approaches, making it possible to calculate forest resource estimates at the subnational level without increasing the costs.
Volume models for single trees in tropical rainforests in Tanzania
(Journal of Energy and Natural Resources, 2014) Masota, Abel Malyango; Zahabu, Eliakimu; Malimbwi, Rogers Ernest; Bollandsås, Ole Martin; Eid, Tron Haakon
The present study was the first to develop total tree, stem and branches volume models for rainforests in southeastern Africa based on destructive sampling. The number of sample trees was 60 and diameter at breast height (dbh) and total tree height (h) ranged from 6 to 117 cm and from 6.4 m to 50 m, respectively. Large parts of the total volume and stem volume variations were explained by the models (Pseudo-R2 ranged from 0.85 to 0.93) and they performed relatively well over different size classes. When considering the challenges in height measurements in rainforests, we in general recommend applying model 3 with dbh only as independent variable. For large trees we recommend model 2 (dbh and h as independent variables) because of the moderating effect h has on volume predictions. If accurate stem volumes are needed for forestry licensing or for calculating compensation of timber loss, we also recommend model 2. As long as the allometry of the trees obviously is not different from that of our study site, the developed models may also be applied for rainforests elsewhere in Tanzania, but further testing of the models is also recommended.