Quantifying and understanding carbon storage and sequestration within the Eastern Arc Mountains of Tanzania, a tropical biodiversity hotspot

Abstract

BackgroundThe carbon stored in vegetation varies across tropical landscapes due to a complex mix of climatic and edaphic variables, as well as direct human interventions such as deforestation and forest degradation. Mapping and monitoring this variation is essential if policy developments such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation) are to be known to have succeeded or failed.ResultsWe produce a map of carbon storage across the watershed of the Tanzanian Eastern Arc Mountains (33.9 million ha) using 1,611 forest inventory plots, and correlations with associated climate, soil and disturbance data. As expected, tropical forest stores more carbon per hectare (182 Mg C ha-1) than woody savanna (51 Mg C ha-1). However, woody savanna is the largest aggregate carbon store, with 0.49 Pg C over 9.6 million ha. We estimate the whole landscape stores 1.3 Pg C, significantly higher than most previous estimates for the region. The 95% Confidence Interval for this method (0.9 to 3.2 Pg C) is larger than simpler look-up table methods (1.5 to 1.6 Pg C), suggesting simpler methods may underestimate uncertainty. Using a small number of inventory plots with two censuses (n = 43) to assess changes in carbon storage, and applying the same mapping procedures, we found that carbon storage in the tree-dominated ecosystems has decreased, though not significantly, at a mean rate of 1.47 Mg C ha-1 yr-1 (c. 2% of the stocks of carbon per year).ConclusionsThe most influential variables on carbon storage in the region are anthropogenic, particularly historical logging, as noted by the largest coefficient of explanatory variable on the response variable. Of the non-anthropogenic factors, a negative correlation with air temperature and a positive correlation with water availability dominate, having smaller p-values than historical logging but also smaller influence. High carbon storage is typically found far from the commercial capital, in locations with a low monthly temperature range, without a strong dry season, and in areas that have not suffered from historical logging. The results imply that policy interventions could retain carbon stored in vegetation and likely successfully slow or reverse carbon emissions.Electronic supplementary materialThe online version of this article (doi:10.1186/1750-0680-9-2) contains supplementary material, which is available to authorized users.

Land cover change and carbon emissions over 100 years in an African biodiversity hotspot

“…Applying the carbon values to the modern day (2000) land cover map results in landscape‐scale carbon estimates similar to comparable regional estimates presented elsewhere in the literature (Willcock et al ., , ), but larger than most globally derived estimates [Baccini et al . (, ), Saatchi et al .…”

Miombo Woodlands Research Towards the Sustainable Use of Ecosystem Services in Southern Africa

“…The author concluded that avoided forest degradation at the study sites would have increased standing woody biomass up to 4.0 t ha -1 year -1 over the 22-year period. Recently, [45] found that carbon storage in the tree-dominated ecosystems of the Tanzanian Eastern Arc Mountains has decreased at a mean rate of 1.47 Mg C ha -1 yr -1 (ca. 2% of the stocks of carbon per year) due to 74% forest area loss driven by 5-fold increase in cropland area.…”

“…Woody biomass was observed to range from 1.5 Mg ha -1 (3-6 years old coppice) to 144 Mg ha -1 (mature wet Miombo) [9,[41][42][43][44][45]. Dry Miombo ranges between 53-55 Mg ha -1 [45][46][47][48]. It is confirmed that wood and soil compartments are the most important of these stocks [48][49], but grass, litter and root may contribute significantly to carbon sequestration.…”

“…This has been mainly associated to: i) soil fertility and plant nutrition; ii) fires and herbivory; and iii) age and status of the woodland. Woody biomass was observed to range from 1.5 Mg ha -1 (3-6 years old coppice) to 144 Mg ha -1 (mature wet Miombo) [9,[41][42][43][44][45]. Dry Miombo ranges between 53-55 Mg ha -1 [45][46][47][48].…”

The impact of animals on crop yields in Malawian rural villages

“…Additionally, it is recognised that there are relatively few studies from the direct study area, or even from Malawi as a whole. Future studies could use weighted means, giving more influence to values geographically nearer to the study area (Willcock et al, 2014;Willcock et al, 2012).…”