Carbon Balance and Management(2)

Background

Deforestation is considered the second largest source ofgreenhouse gas (GHG) emissions amounting to an esti-mated 2 gigatonnes of carbon (GtC) per annum over thelast decade [1]. It is a persistent problem. The UN Foodand Agriculture Organization, in its recently released mostcomprehensive assessment of forests ever, puts deforesta-tion at about 12.9 mil. ha per year [2]. At the same time,forest planting, landscape restoration and natural expan-sion of forests reduce the net loss of forest area. Netchange in forest area in the period 2000–2005 is esti-mated at -7.3 million hectares per year [2]. This reducesthe annual GHG emissions to an estimated 1.1 GtC. Incomparison, 7.3 GtC were emitted in 2003 by using fossilenergy sources [3].

Deforestation has been difficult to tackle by governments,as its drivers are complex and many land uses yield higherrevenues than those from forested land. Some see climatepolicy as a new opportunity to effectively reduce a majorsource of greenhouse gases and biodiversity loss as well asto increase incomes of many people in rural areas whoselivelihood depends on forests. The implementation ofmeasures avoiding deforestation would require innova-tive financial mechanisms in the context of global climatepolicies. In this paper we study the potential magnitude ofeffects of different financial mechanisms to help reducedeforestation, using a modeling approach.

To estimate the impact of financial incentives, to reducedeforestation and assuming profit maximizing behavior,we calculate differences in net present value of differentland uses using a spatially explicit integrated biophysicaland socio-economic land use model. Key model parame-ters, such as agricultural land use and production, popu-lation growth, deforestation and forest productconsumption rates were calibrated against historical nd use changes are simulated in the model as a decisionbased on a difference between net present value of incomefrom production on agricultural land versus net presentvalue of income from forest products. Assuming fixedtechnology, the model calculates for each 0.5° grid cellthe net present value difference between agricultural andforest land-uses in one-year time steps. When carbon mar-ket prices, transferred through a financial mechanism, bal-ance out differences between the net present value ofagricultural land and forest-related income, it is assumed,consistent with profit maximising behavior, that deforest-ation is avoided.

The net present value difference of forest versus other landuses can be balanced out through two mechanisms. Oneis to reduce the difference by adding costs to conversionthrough taxing emissions from deforestation, e. g.through a land clearance tax and wood sales taxes. The

other is to enhance the value of the existing forest byfinancial support when keeping the forest carbon stock, tobe paid in certain time intervals. In both cases the value offorest carbon stock would be pegged to carbon marketprices. The modeling results for different hypothetical taxor subsidy levels show the potential magnitude of avoideddeforestation through financial incentive or disincentivemechanisms. The model results are annual, spatiallyexplicit estimates of the forest area and biomass develop-ment from 2000 to 2100, with particular focus on theperiod 2006 to 2025.

Results and discussion

Baseline deforestation 2000–2100 and effects of financial mechanisms aiming at cutting emissions in half

Baseline scenario calculations (i.e. a carbon price of 0US$/tC is assumed) show that close to 200 mil ha oraround 5% of todays forest area will be lost between 2006and 2025, resulting in a release of additional 17.5 GtC tothe atmospheric carbon pool. The baseline deforestationspeed is decreasing over time, which is caused by adecreasing forest area in regions with hight deforestationpressure. In the year 2025 the annual deforested areadecreases to 8.2 million hectares, compared to 12.9 mil-lion hectares in 2005. By the year 2100 deforestation ratesdecline to some 1.1 million hectares. According to thebase line scenario, today's forest cover will shrink byaround 500 million hectares or by more than 1/8 withinthe next 100 years (figure 1).

Carbon emissions from deforestation in 2005 is 1.1 GtC/year and decreases to 0.68 GtC/year in 2025 and further

Figure 1

Deforested Area until 2100. Deforested Area under alternative assumptions. Incentives... Periodic payments for standing biomass, Tax... Payments for harvesting wood, Burn... felled wood is burned immediately, Sell... harvested wood is soled, Burn/Sell... share of the wood will be burned the other part soled.

to 0.09 GtC/year in 2100. The accumulated carbon releaseduring the next 100 years amounts to 45 GtC which is15% of the total carbon stored in forests today. To bringdeforestation down by 50%, incentives of 6 US$/tC/5 yearor a land clearance tax of between 9 US$/tC and 25 US$/tC would be necessary, depending whether the harvestedwood is burned on the spot (e. g. slash-and-burn agricul-ture) or sold. In the latter case, a higher carbon tax of upto 25 US$/tC is necessary to effectively reduce incentivesto deforest, to a degree that cuts overall global deforesta-tion by 50%. If the wood is further used and convertedinto products, only 18% of the biomass could be saved bya carbon price of 9 US$/tC, caused by the compensatingeffect of an income by selling wood and a longer time-period for releasing carbon. On the other hand, if the car-bon price is 25$/tC and the wood is assumed to be slashburned, the reduction of deforestation calculated to be91% (figure 1 and 2). On a first sight it seems, that incen-tive payments might be more effective, than taxation.However, incentives payment contracts have to berenewed every 5 year for the actual standing biomass andthe change of biomass has to be known to detect a breachof the contract, while a deforestation tax …… 此处隐藏：6005字，全部文档内容请下载后查看。喜欢就下载吧 ……