Category Archives: Abby Cheitlin

Land-Use Change and Its Impact on Carbon Sequestration in Southeastern Spain: Implications for Land Management

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Forest ecosystems are vulnerable to change because human activity causes profound changes in land-use configuration and thus to carbon stocks in the forests and carbon emissions into the atmosphere. To formulate policies that address climate change, carbon sequestration in various types of ecosystems must be monitored because they act as net carbon sinks, fixing more carbon dioxide than they release back into the atmosphere. To provide a basis for measuring implications of land-use change on carbon sequestration services, Padilla et al. (2010) explored the intense changes in land use and potential associated carbon sequestration in the last century in southeast Spain. These changes had important consequences for carbon sequestration and, through this research, the importance of protecting forests for carbon stocks is demonstrated and can be used in policy making. — Abby Cheitlin
Padilla, F. M., Vidal, B., Sánchez, J., Pugnaire, F., 2010. Land-use changes and carbon sequestration through the twentieth century in a Mediterranean mountain ecosystem: Implications for land management. Journal of Environmental Management 91, 2688–2695.
           

Francisco M. Padilla and colleagues explored land-use changes and associated carbon sequestration that occurred through the 20th century in a rural area of southeast Spain. They observed that forest systems replaced dry land farming and pastures from the middle of the century onwards because of agricultural abandonment and afforestation programs. The area, which acts as a carbon sink, saw an increase in carbon stocks following the conversion of farmland to woodland. The authors carried out a land-use classification, determined carbon sequestration rates for the different types of land-use classes, and finally integrated total carbon stock of the different land-use units based on carbon sequestration rates. The area studied in Spain covered


Including Fire Incidences in Amazonian Forests in the Implementation of REDD

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If the reduction of emissions from deforestation and degradation (REDD) is to succeed in reducing carbon emissions, it must include policies to limit fire incidence in tropical forests. REDD includes many policies that will curb carbon emissions, but the consequences for fire hazard are poorly understood. Aragao et al. (2010) analyzed satellite-derived deforestation and fire data from the Brazilian Amazon and the results showed an increase in fire occurrence in the area that has experienced reduced deforestation rates, suggesting that fire-free land management reduces fire incidence and that if sustainable fire-free land-management of deforested areas is not implemented in REDD, the carbon emissions decreased by reducing deforestation will be negated by increased emissions from fires. — Abby Cheitlin
Aragao, L. E. O. C., Shimabukuro, Y. E., 2010. The Incidence of Fire in Amazonian Forests with Implication for REDD. Science 328, 1275–1278.

Luiz E. O. C. Aragao and colleagues used all available data from the National Institute for Space Research (INEP) in Brazil to design a pixel-based analysis of temporal trends in deforestation rates and fire incidence. In addition, the annual number of fires between 1998 and 2006 was derived and the frequency distributions of pixel-based fire trends associated with positive and negative deforestation trends were analyzed. These tests were completed in order to evaluate whether the fire incidence was increasing or decreasing.
The deforestation analyses revealed a widespread pattern of grid cells with negative slopes, which indicates that deforestation rates are decreasing in most of the Brazilian forests within this time period. The fire analyses, on the other hand, showed a reverse pattern with the number of grid cells with positive slopes increasing. The researches were able to analyze fire incidence trends in areas with increased and decreased deforestation rates by combining the deforestation and fire trend results. The majority of grid cells with increased deforestation rates overlap grid cells with positive fire trends, which confirms that fire occurrence increases with deforestation; The majority of grid cells with decreased deforestation rates show increased fire frequency. In order to evaluate the potential of land management in regulating fire in the Amazon, a space-for-time substitution analysis was used. From the study, the authors found that fire incidence is higher when land starts to be cleared for agriculture, because once it is completely cleared there is nothing left to burn. Fire incidence shows declining trends when intensive landuse begins to dominate the landscape beyond the 35% cover threshold, however, high fire incidence is maintained with the increase in total agricultural area. Two conclusions about appropriate new policies can be drawn from this study. First, continual expansion of agrobusiness can drive fire increase in Brazil and therefore must be restricted in order to prevent carbon emissions. Second, changing land-management practices in already deforested areas by using fire-free methods can drastically reduce fire activity and reduce carbon emissions. This study suggests that in order for REDD to be completely successful in reducing carbon emissions into the atmosphere, fire use in the Amazon region must be regulated and monitored more closely. Failure to tackle fire use may negate efforts made through REDD as carbon preservation through decreased deforestation may be outweighed by carbon losses resulting from fire.

Cambodia Case Study—Reducing Emissions While Helping Developing Countries Achieve Sustainable Development to Implement New Climate Change Mechanisms

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Promoting sustainable forest management as part of the mechanism for reducing emissions from deforestation and degradation in developing countries (REDD+) is a necessary component to future policy-making and implies that tropical forests will be considered in new climate change agreements following the end of the Kyoto Protocol term in 2012. Sasaki et al. (2010) conducted a study to assess the costs and revenues on a hypothetical 1-ha tract of tropical forestland in Cambodia against six land use options to propose measures of compensation. Cambodia’s forests are of high management priority if financial incentives through carbon payment are made available. Using annual equivalent values for each landuse option the authors found that the BAU-timber and REDD+ management options were the most financially and environmentally beneficial. These findings suggest that financial incentives that would allow the continuation of sustainable logging while protecting forest carbon stocks should be provided and would be attractive to REDD+ project developers. — Abby Cheitlin
Sasaki, N., Yoshimoto, A., 2010. Benefits of tropical forest management under the new climate change agreement—a case study in Cambodia, Environmental Science & Policy 13, 384–392.

In order to make new policies under REDD+ attractive for implementation, sustainable forest management in the tropics will be promoted to include sustainable timber production and other ecosystem services. Financial incentives that would be made available under REDD+ policies must be comparable to incentives from other land use options. In Cambodia, forested lands are granted as land concessions for industrial plantations without proper long-term financial assessment from each land use option.
Nophea Sasaki and colleagues in Japan conducted a study in which they analyzed forest inventory data and estimated net present value (NPV) and annual equivalent value (AEV) from timber harvesting and compared them with values from other land uses. AEV was used so that potential revenues could be compared on a yearly basis. This is an important tool for measuring investment performance in land use projects. Using their results, the researchers suggested policy directions for implementing REDD+ projects. A hypothetical 1-ha of forest land in Cambodia was assessed against six landuse options: business-as-usual timber harvesting (BAU-timber), forest management under the REDD+ mechanism, forest-to-teak plantation, forest-to-acacia plantation, forest-to-rubber plantation, and forest-to-oil palm plantation. Sasaki et al. found that the total benefit from logging under BAU-timber would be $2173 ha-1 year-1, logging under REDD+ would be $2400 ha-1 year-1, forest-to-teak would be $958 ha-1 year-1, forest-to-acacia would be $688 ha-1 year-1, forest-to-rubber would be $1200 ha-1 year-1, and forest-to-oil palm would be $747 ha-1 year-1. Forest-to-acacia is not profitable at all because the mean annual growth increment for acacia is low in Cambodia. Converting natural forests to oil palm plantations is not profitable as the total annual revenue for oil palm is $852 ha-1 year-1, which would result in a total loss of AEV’s. Ultimately the economic return for managing natural forests is influenced by costs and timber and carbon prices. Under BAU timber, logging companies see a loss because of the market price of timber; however, government revenues are positive because taxes are based on the amount of timber harvested. Under REDD+ management the economic return is higher than for other land use options in Cambodia. This difference in economic return depends on carbon prices and therefore may fluctuate. Reducing emissions while helping developing countries achieve sustainable development is very important for implementing new climate change mechanisms such as REDD+.

The Progress and Challenges for the Implementa-tion of REDD+ in Tanzania

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New mechanisms for conserving forests to reduce negative impacts caused by climate change are needed. Reducing Emissions from Deforestation and Degradation (REDD) is a proposed policy to reduce carbon emissions into the atmosphere from anthropogenic forces such as logging and agriculture. Tanzania is one of the nine pilot countries for the United Nations REDD+ program and receives significant funding from outside governments and the World Bank. These outside sources have come together in attempt to mitigate greenhouse gas emissions, provide income to rural communities and conserve the ecosystem in Tanzania. In order for REDD+ to succeed in Tanzania, there are many improvements and changes in forest management that must be made. N. D. Burgess et al. (2010) conducted a case study of the progress and challenges Tanzania will face in getting ready for the implementation of REDD+. Even in a country with a lot of donor support, established forest management policies, and developed locally-based forest management approaches, there are many challenges. The potentially successful establishment of REDD+ in Tanzania would serve as a good template for other developing countries, but the difficulties of establishing it also highlight the many challenges other countries must deal with preceding REDD+ implementation. — Abby Cheitlin
Burgess, N. D., Bahane, B., Clairs, T., Danielsen, F., Dalsgaard, S., Funder, M., Hagelberg, N., Harrison, P., Haule, C., Kabalimu, K., Kilahama, F., Kilawe, E., Lewis, S. L., Lovett, J. C., Lyatuu, G., Marshall, A. R., Meshack, C., Miles, L., Milledge, S. A. H., Munishi, P. K. T., Nashanda, E., Shirima, D., Swetnam, R. D., Willcock, S., Williams, A., Zahabu, E., 2010. Getting ready for REDD+ in Tanzania: a case study of progress and challenges, Fauna & Flora International, 44(3), 339–351.

Neil D. Burgess and colleagues conducted a study to determine the many challenges Tanzania will face in implementing REDD+. Human destruction of tropical forests is accelerating global warming due to the carbon emissions it releases into the atmosphere. REDD+ is the original concept of REDD with the new addition of sustainable management of forests and conservation to increase forest carbon stocks. REDD+ is an international move to address global warming. The participation of developing countries in REDD+ is important because of their large proportion of the world’s forests. The researchers chose to look at Tanzania as a model for other developing countries because of its already established donor funding to help create REDD+.
The authors discovered many challenges Tanzania will face in the implementation of REDD+. As a country it lacks data and technical capacity, coordination at the national level, and guidelines on how to implement market-oriented methods in either centralized or decentralized government agencies. The Tanzanian government is in favor of taking a fund-based approach to finance the dispersal of REDD+ incentive payments. This would fit with the current land ownership system in Tanzania but would reduce opportunities for the private sector. Burgess et al. came up with four ways that sustainable forest management could be implemented: state-owned protected areas, community forestry approaches, the promotion of agroforestry and conservation agriculture, and state-owned plantations and private forestry. Thus, the ownership and control over land and forests in Tanzania are of great importance in implementing REDD+. Sixteen million of the 35 million ha of forest are on village lands and unreserved. This is a big obstacle in the success of REDD+ in developing countries. Right now, Tanzania is establishing a national forest inventory that will map remote sensing data for the forests. This inventory will provide important calculations of forest cover, forest loss, and hence, emissions levels.

A number of challenges need to be overcome if REDD+ is to be successfully implemented in Tanzania, although the country has made a large effort to prepare for REDD+ and will be embarking on pilot projects in 2010 driven by donor funding.

Pan-tropical Climate Change: Predicting Carbon Stock Gains and Losses due to Rates of Defore-station

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Providing incentives to reduce deforestation and greenhouse gas emissions in countries with tropical forests can be a key action to limit anthropogenic climate change. Deforestation is a major threat to tropical forests globally and accounts for 12 –20% of global carbon emissions into the atmosphere. Tropical deforestation is driven by agricultural practices, logging, and mining, all of which are amplified by population growth, agricultural subsidies, and infrastructure investment. Climate change is also considered a possible risk for the loss of forest carbon stocks. Policies to reduce emissions from deforestation and forest degradation (REDD) strive to ensure permanence, establish reference emission levels, and a measuring, reporting, and verification system. Gumpenberger et al. (2010) used a dynamic global vegetation model (LPJ DVM) to assess the combined impacts of climate and land-use change on tropical forest carbon stocks in pan-tropical countries globally. They found that even under complete cessation of deforestation after 2012, some countries will continue to lose carbon stocks due to climate change. Contrarily, it was found that strong protection of forests could increase carbon stocks in tropical forests due to CO2 fertilization effects.–Abby Cheitlin
Gumpenberger, M., Vohland, K., Heyder, U., Poulter, B., Macey, K., Rammig, A., Popp, A., Cramer, W., 2010. Predicting pan-tropical climate change induced forest stock gains and losses—implications for REDD. Environmental Research Letters 5, 1–15.

Marlies Gumpenberger and colleagues at the Potsdam Institute for Climate Impact Research in Germany used the advanced dynamic global vegetation model (LPJmL) to predict the success of REDD in terms of deforestation against the background of different climate change scenarios in various pan-tropical countries under two different scenarios. In the first scenario, forests are completely protected everywhere from 2012 onwards. In the second scenario, half of the forest area existing in 2012 is deforested, at a constant rate, by 2100. This is a reasonable modeling approach because future changes in forests cannot be predicted linearly from current observations. The scientists based their baseline simulation on historical rates of deforestation, rainfall, and soil carbon stock over the last century. The LPJmL model provides perspective on the combined effects of increasing levels of CO2 in the atmosphere, water cycling, and global warming on plant productivity. Nine plant functional types represented natural vegetation in the study. Except for Bhutan, Nepal, and Pakistan, all countries involved in the study were at least partially located within the tropics.
The results of this study show that vegetation carbon stocks in pan-tropical regions ranged between 154 and 291 Pg C in the last 100 years, and overall, carbon stocks decreased during this time, reaching a minimum in 1990. Under the forest protection scenario, carbon stocks in the tropics increased in the simulations due to CO2 fertilization. Under the deforestation scenario, carbon stocks decreased. Without deforestation, tropical carbon pools would stabilize to higher levels than today with an increase ranging from +7 Pg C to +121 Pg C. The study found, however, that without an increase in CO2 concentrations during the next 100 years, rising temperature (under climate projections) would trigger high tree mortalities rates from heat stress, ultimately causing a decrease in carbon stocks, even without deforestation.

Pattern of Forest Degradation and Carbon Stock Loss in Tanzania can Help Enable Spatially Targeted REDD Policies

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Tropical forest degradation is a large driver of global climate change as it emits carbon into the atmosphere, reduces biodiversity, and assists forest clearance. The new policy program to reduce emissions from deforestation and degradation (REDD) focuses on addressing deforestation. In order to properly formulate possible policy interventions on managing forests to mitigate climate change, degradation drivers and patterns must be more thoroughly understood. Economic theory was used to predict systematic allocation of lands to its highest use value in response to distance from centers of demand. Economic theory was used to see if forest exploitation would expand through time as concentric waves, with each wave targeting lower value products (Ahrends et al., 2010). The researchers concluded that high-value logging expanded over time and forest carbon stocks decreased. The study shows that tropical forest degradation can be followed and predicted, and therefore used to construct policies for addressing climate change and extracting resources without unsustainably reducing forest carbon stocks. —Abby Cheitlin
Ahrends, A., Burgess, N. D., Milledge, S. A. H., Bulling, M. T., Fisher, B., Smart, J. C. R., Clarke, G. P., Mhoro, B. E., Lewis, S. L., 2010. Predictable waves of sequential forest degradation and biodiversity loss spreading from an African city. PNAS 107, 14556–14561.

            Antji Ahrends and colleagues used Economic theory—a theory that provides a general model to predict forest degradation patterns. It was used to test economic resource use theory predictions against ground observations of forest degradation in Dar es Salaam (DES) in Tanzania. The study was preformed along a 210–km transect running south from the center of the city over a period of 14 years (1991–2005). The types of extractive activities occurring in that area was observed and timber depletion as well as logging expansion of those areas were monitored during this time period. In addition to the Economic theory, extraction results were coupled with the loss of carbon stocks and biodiversity as the two are observably linked—depletion of timber results in the decline of forest carbon storage and the species that depend on it.
            In accordance with the Economy theory, Ahrends et al., 2010, found three consecutive degradation waves emanating from the center of DES. The innermost wave contained the lowest value timber, while the outermost wave contained the highest value timber. The order of concentric degradation waves remained the same over the 14 years; however, each wave significantly increased in size by 2005. This pattern is predicted to continue if nothing is done to stop it because as forests are exhausted, charcoal production is likely to move further from the center point to obtain more timber. This combined with the observed increase in mean harvested tree size is indicative of unsustainable harvesting practices in Tanzania.
            The results from the study are troubling as between 1991 and 2005 there were major declines in tree density, carbon stocks, and mean tree size in Tanzanian forests. The research completed provides three important insights to the implementation of REDD and other policies on climate change: deforestation waves should be represented in models of the “opportunity costs” of avoiding degradation, carbon fluxes from degradation are significant, and models of degradation dynamics may identify areas that are more vulnerable to carbon loss, enabling spatially targeted REDD policies and incentives.

Estimates for Rainforest Biomass Stocks and Carbon Loss from Deforestation and Degradation in Papua New Guinea Over a Thirty-Year Period

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Tropical logging and deforestation is a large contributor to global greenhouse gas emissions and is one of the most uncertain components to climate change models. It is imperative that this uncertainty is reduced as providing incentives to slow deforestation is a cost-effective way of mitigating the impacts of global warming. The reduction of emissions from deforestation and degradation (REDD) has been a good way of reducing global greenhouse emissions so far. In order for effective measurements to reduce forest loss to be put in place data on forest cover change and biomass is necessary. A field-based study by Bryan et al. (2010), was done to estimate tropical forest carbon stocks and losses between the years 1972 and 2002 in Papua New Guinea (PNG). This country has one of the world’s largest remaining tropical forest areas. Using the best available literature and data to calculate rainforest carbon stocks as well as emissions from logging, plot-level estimates across Papua New Guinea were extrapolated using high-resolution forest mapping. Through the research they discovered many loopholes and uncertainties; however, they found that, for such a small and rural population, PNG is a strikingly large contributor to global tropical emissions due to land-use change. They found that emissions from logging in PNG rose from 21% in 1972 to 41% in 2002. This drastic increase in pollution indicates that management of the forest industry in PNG should be a priority if the country is to participate in REDD starting in 2012, following the end of the Kyoto Protocol term. —Abby Cheitlin
Bryan, J., Shearman, P., Ash, J., and Kirkpatrick, J. B., 2010. Estimating rainforest biomass stocks and carbon loss from deforestation and degradation in Papua New Guinea 1972–2002: Best estimates, uncertainties and research needs. Journal of Environmental Management, 91, 995–1001.

            Jane Bryan and colleagues determined forest biomass and carbon stocks in PNG by extrapolating field measurements of biomass using forest mapping and environmental data. Forest carbon losses were computed using the measured, deforested area in combination with extrapolated forest biomass measurements. The forest mapping was conducted using a semi-automated forest classification procedure that used high-resolution satellite imagery and aerial photography. The researchers collated 22 published estimates of unlogged biomass as well as 11 full tree censuses from across PNG. Allometric equations based on wood density, height, and diameter was used to predict aboveground biomass from each tree in the 11 forests. Annual mean temperature for each forest area was estimated, but no significant relationship between ambient temperature and biomass quantity was found. To assess uncertainty in the unlogged forest estimates, the PNG biomass measurements were compared to those from other tropical regions. The authors added their best calculations of logged and unlogged biomass together to get an estimation of PNG biomass stocks in 2002. Next, they added their ‘upper’ predictions of logged and unlogged biomass stocks to produced an ‘upper’ prediction of rainforest biomass stocks in 2002. The same was done with their ‘lower’ estimates. To find the amount of carbon from biomass, biomass stocks were multiplied by 0.5 because about 50% of biomass is carbon. The amount of carbon released by deforestation in PNG in the 30 year time period was determined using high-resolution maps of the deforested area. Calculating biomass killed due to degradation required calculating potential unlogged biomass within the degraded area. Finally, multiplying the annual biomass loss by 0.5 projected annual carbon loss.
            The best estimates of total gross biomass and carbon loss in the 30 years were 2356 and 1178 Metric tons. Carbon release due to anthropogenic causes rose from 24 Mt to 53 Mt in 30 years, with logging accounting for 21% of total emissions in 1972 to 41% in 2002. The results suggest that it is possible to generate a range of calculations for carbon storage and flux; however, there remains a high degree of uncertainty regarding their actual values. The measurement of biomass in many more locations across PNG is necessary and many more logging damage studies with pre-logging as well as post-logging biomass measurements are needed in order to accurately measure carbon losses through degradation. If PNG is serious about participating in the REDD process, they need to prioritize the implementation of a large-scale program of forest biomass measurement in unlogged forest.

Elevated Amazon Forest Tree Mortality Associated with Convective Storm Processes

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A better understanding of forest disturbances linked to convective storm processes is needed given the increase in heavy precipitation cycles in the Amazon forest due to anthropogenic climate change. If a warming climate increases storm intensity and frequency, forest mortality may increase as well, resulting in greater carbon release into the atmosphere and further warming of the climate system. Negrón-Juárez et al. (2010) investigated forest disturbance produced by the storm to prove that a single squall line across the Amazon in January of 2005 caused widespread tree mortality, which may have caused the higher tree mortality that year. It is projected that it killed 0.3–0.5 million trees that year, equivalent to 30% of the annual deforestation. The results demonstrate the vulnerability of the trees in the Amazon to wind-driven mortality. –Abby Cheitlin
Negrón-Juárez, R. I., Chambers, J. Q., Guimaraes, G., Zeng, H., Raupp, C. F. M., Marra, D. M., Ribeiro, F. H. P. M., Saatchi, S. S., Nelson, B. W., and Higuchi, N. (2010), Widespread Amazon forest tree mortality from a single cross-basin squall line event, Geophys. Res. Lett., 37, 1–5.

Robinson I. Negrón-Juárez and colleagues used Landsat images from Brazil’s National Institute for Space Research covering the Manaus area to complete the study. Tree mortality was calculated by subtracting images of per-pixel fractional abundance of green vegetation, non-photosynthetic vegetation, soil, and shade taken in October of 2004 from images taken in July of 2005. Two approaches were used to estimate tree mortality and biomass loss. The first was Landsat-derived change in non-photosynthetic vegetation (∆NPV) combined with above ground biomass distribution map. The second approach was a Monte Carlo (MC) simulation model, which used a distribution function for stem density and tree biomass generated from permanent forest inventory plots. The study linked tree mortality date, remote sensing analyses, and an empirical model to quantify tree mortality in the Amazon produced by a squall line in January of 2005.
Squall lines are clusters of convective cells that cause heavy rainfall during the dry season, and high wind velocities sufficient to generate forest blowdowns. Although anthropogenic causes are responsible for deforestation and carbon greenhouse gases in the atmosphere, natural events can severely disturb forests as well. The study shows a strong relationship between Landsat ∆NPV and field-measured tree mortality. Widespread forest disturbance by a single squall line in 2005 must have been a contributing factor to the unusually high tree mortality that year.

Pan-tropical Climate Change: Predicting Carbon Stock Gains and Losses due to Rates of Deforestation

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Providing incentives to reduce deforestation and greenhouse gas emissions in countries with tropical forests can be a key action to limit anthropogenic climate change. Deforestation is a major threat to tropical forests globally and accounts for 12­­­–20% of global carbon emissions into the atmosphere. Tropical deforestation is driven by agricultural practices, logging, and mining, all of which are amplified by population growth, agricultural subsidies, and infrastructure investment. Climate change is also considered a possible risk for the loss of forest carbon stocks. Policies to reduce emissions from deforestation and forest degradation (REDD) drive to ensure permanence, establish reference emission levels, and a measuring, reporting, and verification system. Gumpenberger et al. (2010) used a dynamic global vegetation model (LPJ DVM) to assess the combined impacts of climate and land-use change on tropical forest carbon stocks in pan-tropical countries globally. They found that even under complete stop of deforestation after 2012 some countries will continue to lose carbon stocks due to climate change. Contrarily, it was found that strong protection of forests could increase carbon stocks in tropical forests due to CO2 fertilization effects. –Abby Cheitlin
Gumpenberger,  M., Vohland,  K., Heyder, U., Poulter,  B., Macey, K., Rammig,  A., Popp,  A., Cramer, W., 2010.  Predicting pan-tropical climate change induced forest stock gains and losses—implications for REDD. Environmental Research Letters 5, 1–15.

Marlies Gumpenberger and colleagues at the Potsdam Institute for Climate Impact Research in Germany used the advanced dynamic global vegetation model (LPJmL) to predict the success of REDD in terms of deforestation against the background of different climate change scenarios in various pan-tropical countries under two different scenarios. In the first scenario, forests are completely protected everywhere from 2012 onwards. In the second scenario, half of the forest area existing in 2012 is deforested, at a constant rate, by 2100.  This is the most accurate approach because future changes in forests cannot be predicted linearly from current observations. The scientists based their baseline simulation on historical rates of deforestation, rainfall, and soil carbon stock over the last century. The LPJmL model provides perspective on the combined effects of increasing levels of CO2 in the atmosphere, water cycling, and global warming on plant productivity. Nine plant functional types represented natural vegetation in the study. Except for Bhutan, Nepal, and Pakistan, all countries involved in the study were at least partially located within the tropics of Cancer and Capricorn.
            The results of this study show that vegetation carbon stocks in pan-tropical regions ranged between 154 and 291 Pg C in the last 100 years, and overall, carbon stocks decreased during this time, reaching a minimum in 1990. Under the forest protection scenario, carbon stocks in the tropics increased in the simulations due to CO2 fertilization. Under the deforestation scenario, carbon stocks decreased. Without deforestation, tropical carbon pools would stabilize to higher levels than today with an increase ranging from +7 Pg C to +121 Pg C. The study found, however, that without an increase in CO2 concentrations during the next 100 years, rising temperature (under climate projections) would trigger high tree mortalities rates from heat stress, ultimately causing a decrease in carbon stocks, even without deforestation.