The carryover of fire activity from forest clearing into subsequent years is a cumulative process, such that total high-frequency fire activity in any year represents burning for multiple years of forest loss . For example, elevated fire activity during 2004 in Mato Grosso is the product of deforestation rates during 2002–2005 and high fire frequencies in 2004 for cropland and pasture deforestation. In general, fire frequency is highest for the year in which the deforestation was mapped. For cropland deforestation, fire frequency is similar in the year before and following deforestation mapping. For pasture deforestation, fire frequency is consistently higher in the year following deforestation mapping than the year before detection of deforestation. The number of days on which fires are detected at the same ground location is higher for areas undergoing deforestation than for other fire types in Amazonia, and fires on 3 or more days at the same ground location are almost exclusively linked with forest conversion. During 2003–2007, more than 40% of all high-confidence MODIS fire detections within Amazonia were associated with deforestation. Within this subset of repeated fire detections, container growing raspberries variations in fire frequency suggest that carbon losses from deforestation vary with postclearing land use. Deforestation for cropland may involve burning on as many as 15 days during the same dry season as woody fuels are piled and re-burned to prepare the land for mechanized agricultural production.
Forest conversion for pasture is characterized by fewer days of burning during the dry season, on average, and fewer years of high-frequency fire detections than conversion to cropland. Forests without evidence for cropland or pasture usage following deforestation detection have the lowest fire activity. Higher fire frequency associated with mechanized deforestation suggests greater combustion completeness of the deforestation process compared with less intensive clearing methods. Whereas the first fire following deforestation may consume 20–62% of the forest biomass depending on fuel moisture conditions , piling and burning trunks, branches, and woody roots many times in the same dry season may increase the combustion completeness of the deforestation process to near 100% . Based on published combustion completeness estimates of 20% or 62% per fire, repeated burning during the deforestation process could eliminate initial forest biomass after 5–22 fire events. Combustion completeness and fire emissions from recent deforestation may be higher than previous estimates for deforestation carbon losses. Mechanized equipment can remove stumps and woody roots in preparation for cropland such that both above and below ground forest biomass are burned. Burning woody roots may increase the fire affected biomass by as much as 20% . Fires that burn piled wood are likely to be at the high end of the published range for combustion completeness, given field measurements of high fire temperature and longer duration of flaming and smoldering stages of combustion in piled fuels compared with pasture or initial deforestation fires . High fire frequency for recent deforestation also generates higher total fire emissions compared with previous estimates that assume that a majority of carbon is lost as CO2 from heterotrophic respiration of unburned biomass .
These attributes of fire use for mechanized deforestation in Amazonia challenge the basic assumptions that monitoring deforested area and estimating above ground biomass of tropical forests are sufficient to estimate carbon emissions from deforestation . Failure to consider the evolving roles of post clearing land use on combustion completeness could introduce substantial uncertainty into calculated reductions in carbon emissions from declines in deforestation rates. Findings in this study suggest that average combustion completeness for recent deforestation may be two to four times greater than that estimated for deforestation during 1989–1998 , increasing per-area gross fire emissions for the current decade by a similar magnitude in regions where mechanized deforestation is common. Deforestation for highly capitalized, intensive agricultural production may also reduce the rates of land abandonment to secondary forest compared with previous periods of Amazon colonization, reducing the offset of gross fire emissions from regrowing forests . In addition to further field measurements, we are currently developing a detailed model representing variations in forest biomass, combustion completeness of new deforestation, and offset of fire emissions from regrowing vegetation to more accurately quantify the influence of agricultural intensification on carbon emissions in the region. The use of heavy equipment to manage forest biomass may also change the nature of trace-gas emissions from deforestation. Emissions factors for CO2 are relatively similar for flaming and smoldering phase combustion, but emissions of CH4, CO, and some VOCs from the smoldering stage of deforestation fires are nearly double than that during the flaming phase . The balance between flaming and smoldering phase combustion for 2nd–Nth fires during the forest conversion process is unknown. If emissions ratios do change during the course of the deforestation process as a function of the size or moisture content of woody fuels, the frequency of satellite-based fire detections provides one method to characterize time-varying trace gas emissions for Amazonia. Combining daytime and night-time observations from multiple sensors may better characterize the duration of individual fires to allow more direct interpretation of satellite data for trace gas emissions.Interannual differences in total and high-frequency fire activity highlight trends in both economic and climate conditions across Amazonia.
Concentrated fire activity in Mato Grosso state during 2003–2004 is consistent with peak deforestation for cropland, driven, in part, by high prices for soybean exports . Carryover of fire activity from previous years’ deforestation also contributes to high fire detections during 2003–2005 in Mato Grosso. Thus, reductions in fire intensive cropland deforestation during 2005 do not result in a shift in fire intensity away from central Mato Grosso state until 2006. Regional differences in concentrated fire activity also highlight the role of climate in mediating human caused fires. Roraima, Acre, and Tocantins states in Brazil show dramatic differences in fire activity during 2003, 2005, and 2007. During drought periods in 2003 and 2005, Roraima and Acre had approximately seven and four times as many fires as under normal climate conditions, respectively. The fraction of high-frequency fires was also highest during these drought years, supporting the results from recent studies showing anomalous fire activity and large areas of burned agricultural land and forest in drought affected areas . Future work to verify the detection of active forest burning by satellites is needed to quantify the contribution of forest fires to the regional patterns of high-frequency fire in drought years. In 2007,raspberries for containers anomalous fire activity was driven primarily by low-frequency fires concentrated in southeastern Amazonia and a return to 2004 levels of deforestation fire activity in southeastern Bolivia and the Brazilian states of Mato Grosso and Para´. These examples suggest that even localized drought conditions can spur anomalous fire activity in the presence of anthropogenic ignition sources for deforestation and agricultural land management with important consequences for gross fire emissions. The timing of fires for forest conversion may influence the likelihood of fires escaping their intended boundaries and burning neighboring forest and Cerrado vegetation. Deforestation for pasture contributes more fires during the late dry season when forests in Mato Grosso state may be most flammable after 3–5 months with little rainfall. More even distribution of fires for cropland clearing throughout the dry season may reduce the risk of forest fires. Different timing for cropland and pasture deforestation fires is consistent with management practices for intensive agriculture; mechanized crop production with chemical fertilizers is less reliant on the ash layer from deforestation fires for soil fertility than cattle pasture or smallholder agriculture land uses. However, deforestation fires for both cropland and pasture in Mato Grosso state were common during July and August of 2003–2005 despite local regulations prohibiting fires during these months to minimize the risk of unintended forest fires . Because the most frequent fire detections are indicative of mechanized deforestation and post clearing land use for intensive agricultural production, monitoring cumulative fire frequency could aid the rapid detection of mechanized forest clearing. Improved geolocation and fire detection capabilities of the MODIS sensors compared with previous satellite instruments enable a higher resolution investigation of these patterns of repeated fire activity.
Despite the moderate resolution of the MODIS sensors, information on fire frequencyat 1-km resolution is commensurate with clearing sizes for mechanized crop production in Amazonia that average 3.3 km2 . Active fire information has not previously been merged with land cover change estimates for deforestation monitoring.Our approach to quantify the contribution of deforestation to satellite-based fire activity and characterize individual forest conversions in terms of fire frequency is intentionally conservative. Because of issues of both omission and commission of fires by the MODIS sensors, it is not possible to determine the exact timing or frequency of all fires for the conversion process. We begin with a high-confidence subset of active fire detections to reduce data errors from spurious fire detections over tropical forest . Next, we link deforestation fire activity to high-frequency fire detections, such that fires must be detected at the same ground location on 2 or more days, despite omission of fires from MODIS attributable to fire size , orbital coverage , and the diurnal cycle of fire activity . Despite well-defined changes in land cover, 12% of cropland and 27% of pasture deforestation events in 2004 showed no fire activity in the high-confidence subset of fire detections. Therefore, low-frequency and omitted fires likely increase the fraction of total fire activity in Amazonia linked to deforestation. Because of omission of active fires by MODIS, a more robust method to estimate combustion completeness of the deforestation process may be to combine active fire detections from multiple sensors with other satellite data on deforestation or vegetation phenology to follow the fate of cleared areas over time.A phenomenon that I term REDD Out Ahead is a recurring theme for both REDD negotiators and REDD policy advocates, but for different reasons. For negotiators, REDD out ahead is indicative of a fear that of a lack of coordination between REDD and other elements of the climate schemes. Several of my interview subjects sees this as stemming in part from a lack of capacity for some parties to monitor all streams of the negotiation. A related concern is the unwillingness or inability to assign sufficiently competent staff to the REDD negotiations themselves. On the flip side, some advocates frame the rapid progress of REDD as a point of pride and evidence that the UNFCCC is a viable venue for climate policy. Another set of advocates and scholars, meanwhile argue that the rapid progress of REDD is indicative of the market orientation of REDD and attendant concerns about issues of environmental justice.Every one of my interview subjects spoke of drivers in a way that evoked agriculture. Despite that fact that agriculture is not at present mentioned in the REDD text, the interviewees suggest that the term “drivers of deforestation” is very nearly a proxy for agriculture. Some subjects see this is development as foundational for the future of REDD. Generally speaking, this camp argues that “stove piping” of land use issues is to be avoided. The concern is that this is inefficient for monitoring, and that “you can’t get there from here”, meaning that reducing tropical deforestation appreciably cannot occur without addressing agricultural issues. However, an even larger portion of the party representatives I interviewed see agriculture as what one interviewee described as the “third rail” of international governance in general and in particular environmental governance. “I know we can’t get there from here without agriculture,” one subject told me, “but look, I am as big an advocate for a new treaty as they come and with agriculture in the mix it’ll never happen.” When pressed, the rationale is that the agriculture deforestation link inherently involves grappling with international trade of agricultural commodities. One respondent described this as a, “$100 billion dollar issue.” Among, advocates, however, there is a strong push to get agriculture on the REDD bandwagon. One advocate describes REDD as the last best chance to revive overseas development assistance for agriculture .For several interviewees, the drivers theme heralds a broader trend in decentralizing the principles and content of REDD. These feelings closely cohere with how Boyd describes the emerging polycentricity of REDD.