Plantation Forests Increase Carbon Storage on Hainan Island, Southern China

by Stephen Johnson

Forested landscapes in the tropics are often highly dynamic, with natural forest being replaced by a shifting mosaic of plantations, agriculture, pasture, and settlements, which are in turn occasionally replaced by ecological restoration. This produces landscapes that vary in their capacity to sequester and store carbon. In South East Asia, as in many parts of the tropics, natural forests are commonly converted to plantations of rubber, Eucalyptus, pine, and hardwood for timber. The carbon storage capacity of a forest depends on the species of trees, which vary in density and size. Consequently, the type of forest, artificial and natural, determines the carbon storage capacity of a landscape. On Hainan Island in Southern China, land cover has been continuously altered over the past century, with artificial plantation forests replacing natural rain forest. Ren et al. (2014) analyzed how carbon storage capacity differs between land use types and how the total quantity of stored carbon has changed through time. Using both remote sensing and forest inventory plots, they quantified the carbon stored in woody vegetation, understory, herbs, leaf litter, and soil in each type of land use. They found that carbon storage capacity is highest in natural forests, and while these forests have been reduced over the years, the proliferation of plantation forests has actually increased the total carbon storage of the island. Furthermore, they found that 75% of the forest’s carbon was stored in soil rather than woody biomass, emphasizing the importance of maintaining soil communities. Continue reading

Measuring Carbon Changes and Future Deforestation

by Maithili Joshi

It is important to maintain tropical forests because of their role as carbon sinks, its vast biodiversity, and vital resources that we commonly use. These important features drive many United Nations policies that protect forests and their abundance of tree species. However, quantifying the usefulness of these polices is difficult. Gonzalez et al.(2014) aimed to quantify tree biodiversity, historical land cover and carbon changes and uncertainties, and lastly project potential future forest carbon changes and uncertainties. This study was conducted in Selva Central, Peru at the western end of the Amazon Basin. Continue reading

Carbon Storage in Restored Forests is Species and Age Dependent

by Stephen Johnson

Deforestation in tropical rainforests is a significant and growing conservation concern, and for good reason: as well as harboring high levels of biodiversity, tropical forests are estimated to store 59% of global terrestrial carbon. The capacity of woody plants to store carbon, which constitutes 50% of their biomass, makes them an indispensible consideration in the effort to mitigate global climate change. Of course, forests can’t store carbon if they don’t exist. In the past 14 years alone, more than 100 million hectares of tropical forest have been lost—an area greater than Texas and Arizona combined. This continued destruction has prompted interest in the ability of ecological restoration—replanting forests—to provide ecosystem services such as carbon sequestration and biodiversity habitat. In attempting to rapidly revitalize damaged ecosystems, fast-growing, pioneer species with low wood density are often chosen to replant, though slower-growing, denser species may be required for long-term carbon storage and ecosystem health. To help resolve this question, Shimamoto et al. (2014) examined the biomass accumulation of ten tree species with different ages and growth patterns. By comparing measurements of fast and slow-growing trees in forests of different ages, they were able to determine carbon sequestration through analysis of covariance tests as well as linear and non-linear models. They found that in the first 35-40 years, fast-growing species accumulate the most carbon, but after 40 years, slow-growing species accumulate more carbon, and older forests overall sequester more carbon than young forests. Continue reading

Oil Palm Plantation Boom in Indonesia

by Chieh-Hsin Chen

The anticipated depletion of fossil fuel has caused the production of alternative fuel sources to become an extremely important field of industry. Many less developed countries in South East Asia promote mass production of biofuel crops as a primary export. Palm oil, used in cooking as well as biofuel, is one of the main exports from Indonesia. The high demand of palm oil has led to a rapid increase of oil palm plantations, leading also to massive deforestation. Riau Province is one of the largest oil palm producing regions. From 1990s to 2012, there has been a significant decrease of forest in the region due to the boom of oil palm plantations. Ramdani and Hino (2013) analyze satellite imagery and greenhouse gas emissions from different time periods to determine the scale of deforestation. The results show that in the Riau Province, the oil palm industry rapidly increased from 1990 to 2000, with transformation of tropical forest and peat land as the primary source of emissions. Continue reading

New comprehensive estimates of consequences due to direct and indirect land use changes in the biofuel industry more accurately highlight necessary policy change.

With the new increases in biofuel production around the world, attention must turn to the potential negative environmental impacts due to altered land use.  Previous estimates of these consequences used models that were not geographically nor ecologically specific and led to gross miscalculations. This case study in Brazil projects the effects on the Amazon due to increased biofuel production using a spatially explicit model to project land-use changes caused by that expansion in 2020 (Lapola et al, 2009).  New estimates reveal that current methods of land use allocation may create a carbon debt that would take up to 250 years to be repaid, an amount which overcomes the carbon sequestering benefits of biofuels over fossil fuels. — Elena Davert
Lapola, D.M., Schaldach, R., Alcamo, J., Bondeau, A., Koch, J., Koelking, C., Priess, J.A.  Indirect land-use changes can overcome carbon savings from biofuels in Brazil.  Proceedings of the National Academy of Science 107, 3388–3393.

 Currently, Brazil’s government, in conjunction with the biofuel industry, is planning a large increase in the production of biofuels over the next 10 years. With the potential ethanol production increase of 35 (4) x 109 liters in the 2003-2020 period –which equates to a projected indirect deforestation of 121,970 km2 by 2020– there are clear concerns about measuring the consequences of the land-use changes (LUC) associated with this increase. Some of the previous studies focused on the direct land-use changes (DLUC) and the resulting “carbon debt” caused by replacing native habitats with biofuel crops, while others pointed to the probable indirect land-use changes (ILUC) in Brazil caused by future expansion of food and biofuel croplands in other countries such as the United States. Although these studies showed that potential LUC must be taken into account to assess the efficacy of a given biofuel, they were neither spatially explicit, nor did they specifically consider competition between different land uses in view of concurrent food and biofuel demands. Because of this, calculations of the effects of LUC in previous studies are mostly underestimated or incomplete.
In order to create as fully comprehensive estimate of effects due to LUC, Lapola et al used a new spatially explicit modeling framework to project the complete DLUC and ILUC resulting from Brazil’s biofuel production targets for 2020.  In addition to being spatially explicit, the new model is also concurrent with increasing food and livestock demands and their demands for land as well. The modeling framework comprises of 3 major components: (1) a land-use/land-cover change model for land-use suitability assessment and allocation; (2) a partial equilibrium model of the Brazilian economy of the agricultural sector for future food demands, livestock demands, and advancement of crop yields due to improved technology; and (3) a dynamic global vegetation model for varying crop and grassland potential productivity driven by climate changes. The competition among land uses –for land resources– is also incorporated into the model based on an evaluation of suitability, hierarchical dominance of major land-use activities (settlement, crop cultivation, livestock grazing), and a land allocation algorithm which looks for land-use pattern stability over multiple land use objectives.
According to the new model, 88% of the DLUC  (145,700 km2) due to sugarcane cropland increasing by 57,200 km2 and soybean cropland increasing by 108,100 km2 will take place in areas previously used as rangeland, and the amount of cropland area replaced by biofuels would reach 14,300 km2. The resulting deforestation amounts to only 1,800 km2 of forest and 2,000 km2 of woody savanna, the required payback time for sugarcane DLUC emissions would be 4 years, while the DLUC carbon emissions for soybean biodiesel would not be paid back for at least 35 years. While these numbers are not considerably daunting, the model revealed that ILUC could considerably compromise the GHG savings from growing biofuels, mainly by pushing rangeland frontier into the Amazon forest and Brazilian Cerrado savanna. With an expansion of 121,970 km2 of rangeland into forest areas, and 46,000 km2 into other native habitats due to the expansion of biofuel croplands, the required payback time for GHG emissions increases to 44 years for sugarcane crops and 246 years for soybean crops.
Ultimately, the dramatic costs of ILUC in this study raise the question of whether the common practice of reallocating all displaced rangeland should continue. Changes in current practices will be difficult because not only is animal acquisition currently heavily subsidized in Brazilian cattle ranching, especially in the Amazon region, but very few incentives are provided for the recovery of degraded pastures. Socioeconomic surveys also suggest that technological innovation or the intensification of livestock inside the Amazon region may increase the attractiveness of cattle ranching and thus further deforestation. The authors argue that in order to avoid the undesired ILUC caused by biofuels, strategies for increased cooperation between the cattle ranching and biofuel-growing sectors should be implemented by the biofuel sector, and institutional links between these two sectors should be strengthened by the Brazilian government.