Paulo Maurício Lima de Alencastro Graça

Testing for criticality in ecosystem dynamics: the case of Amazonian rainforest and savanna fire

We test for two critical phenomena in Amazonian ecosystems: self-organized criticality (SOC) and critical transitions. SOC is often presented in the complex systems literature as a general explanation for scale invariance in nature. In particular, this mechanism is claimed to underlie the macroscopic structure and dynamics of terrestrial ecosystems. These would be inextricably linked to the action of fire, which is conceived as an endogenous ecological process. We show that Amazonian savanna fires display the scale-invariant features characteristic of SOC but do not display SOC. The same is true in Amazonian rainforests subject to moderate drought. These findings prove that there are other causes of scale invariance in ecosystems. In contrast, we do find evidence of a critical transition to a megafire regime under extreme drought in rainforests; this phenomenon is likely to determine the time scale of a possible loss of Amazonian rainforest caused by climate change.

Desmatamento no sul do estado de Roraima: padrões de distribuição em função de projetos de assentamento do INCRA e da distância das principais rodovias (BR-174 e BR-210)

Deforestation in the Amazon currently represents one of the greatest environmental issues in Brazil, and stopping this process requires public policies based on understanding the forces that control the forest loss in different parts of Amazonia. We evaluated deforestation in the southern portion of Roraima State using a Geographical Information System (GIS) to delineate buffers along each of the two main highways that cross the region: BR-174 and BR-210. Each buffer was 20 km wide and was divided into eight strips 2500 m in width. The study covered the 2001-2007 period using annual deforestation data from PRODES vector files and visual analysis of TM Landsat 5 imagery. We also used shape files of roads and settlement projects in the southern part of Roraima coupled with field observations. Deforestation in the period was strongly related to the availability of roads and to the number of families present in the settlement project. The occurrence of deforestation was highest in the area of the BR-210 where large landowners and land invasions were present. The logging center on the BR-174 may have influenced the formation of small clearings in the Rorainopolis city neighbor. Predatory logging and new land occupations by both small and large landholders are spreading quickly in a disorderly fashion. This situation has high potential for forest loss since migration is expected to increase if Roraima is connected to the “Arc of Deforestation” by reopening the BR-319 Highway, which would connect Manaus to Porto Velho.

Deforestation and Carbon Stock Loss in Brazil’s Amazonian Settlements

We estimate deforestation and the carbon stock in 2740 (82 %) of the 3325 settlements in Brazil’s Legal Amazonia region. Estimates are made both using available satellite data and a carbon map for the “pre-modern” period (prior to 1970). We used data from Brazil’s Project for Monitoring Deforestation in Amazonia updated through 2013 and from the Brazilian Biomes Deforestation Monitoring Project (PMDBBS) updated through 2010. To obtain the pre-modern and recent carbon stocks we performed an intersection between a carbon map and a map derived from settlement boundaries and deforestation data. Although the settlements analyzed occupied only 8 % of Legal Amazonia, our results indicate that these settlements contributed 17 % (160,410 km2) of total clearing (forest + non-forest) in Legal Amazonia (967,003 km2). This represents a clear-cutting of 41 % of the original vegetation in the settlements. Out of this total, 72 % (115,634 km2) was in the “Federal Settlement Project” (PA) category. Deforestation in settlements represents 20 % (2.6 Pg C) of the total carbon loss in Legal Amazonia (13.1 Pg C). The carbon stock in remaining vegetation represents 3.8 Pg C, or 6 % of the total remaining carbon stock in Legal Amazonia (58.6 Pg C) in the periods analyzed. The carbon reductions in settlements are caused both by the settlers and by external actors. Our findings suggest that agrarian reform policies contributed directly to carbon loss. Thus, the implementation of new settlements should consider potential carbon stock losses, especially if settlements are created in areas with high carbon stocks.

Caracterização de uso e cobertura da terra na Amazônia utilizando imagens duais multitemporais do COSMO-SkyMed

The use of radar imagery is an alternative source of information to support the monitoring of the Amazon region, since the optical images have imaging limitations in tropical areas due to the occurrence of clouds. Therefore, the goal of this study is to analyze the radar images in X-band multi-temporal polarized obtained by COSMO-SkyMed satellite (COnstellation of small Satellites for Mediterranean basin Observation), in the intensity mode, isolated and/or combined with textural information, to thematic characterization of land use/land cover in the Humaita, Amazonas State region. The methodology used includes: analysis of the dual images obtained during two subsequent acquisitions, in order to explore the potential of the dataset as a quad-pol intensity; extraction of textural attributes from the co-occurrence matrix (Gray Level Co-occurrence Matrix) and subsequent contextual classification; statistical assessment of the thematic performance of the intensity and textural images, isolated and in polarized groups. Within the results achieved, the group formed only by the intensity images presented a better performance if compared to those containing the textural attributes. In this discrimination, the classes involved were forest, alluvial forest, reforestation, savannah, pasture and burned areas, yielding 66% overall accuracy and a Kappa value of 0.55. The results showed that X band images, from COSMO-SkyMed, StripMap mode (Ping-Pong), multi-polarized, presents a moderate potential to characterize and monitor the dynamics of land use/land land cover in the Brazilian Amazon.

Multi-temporal analysis of radiometric changes in satellite images of forest edges to infer selective-logging areas in the Amazon forest

Radiometric changes observed in multi-temporal optical satellite images have an important role in efforts to characterize selective-logging areas. The aim of this study was to analyze the multi-temporal behavior of spectral-mixture responses in satellite images in simulated selective-logging areas in the Amazon forest, considering red/near-infrared spectral relationships. Forest edges were used to infer the selective-logging infrastructure using differently oriented edges in the transition between forest and deforested areas in satellite images. TM/Landsat-5 images acquired at three dates with different solar-illumination geometries were used in this analysis. The method assumed that the radiometric responses between forest with selective-logging effects and forest edges in contact with recent clear-cuts are related. The spatial frequency attributes of red/near infrared bands for edge areas were analyzed. Analysis of dispersion diagrams showed two groups of pixels that represent selective-logging areas. The attributes for size and radiometric distance representing these two groups were related to solar-elevation angle. The results suggest that detection of timber exploitation areas is limited because of the complexity of the selective-logging radiometric response. Thus, the accuracy of detecting selective logging can be influenced by the solar-elevation angle at the time of image acquisition. We conclude that images with lower solar-elevation angles are less reliable for delineation of selecting logging.

Brazil’s Amazonian protected areas as a bulwark against regional climate change

Brazil’s Amazonian protected areas play an important role in maintaining the environmental services of the region, including Amazonia’s role in regional and global climate. These protected areas face threats both from deforestation and from degradation of standing forest. Preserving carbon stocks in protected areas is important both because of the climatic benefit of avoiding greenhouse gas emissions and because of the potential to provide a monetary value that contributes to supporting local human populations in ways that maintain rather than destroy the forest. REDD+ represents one potential mechanism for maintaining these areas. A variety of legal threats to protected areas in Brazilian Amazonia has arisen, leading to concern over the future of these areas and their role as a bulwark against regional climate change.

Deforestation Dynamics on an Amazonian Peri-Urban Frontier: Simulating the Influence of the Rio Negro Bridge in Manaus, Brazil

AbstractPeri-urban expansion is an increasingly important source of tropical deforestation, and a bridge over the Rio Negro in Brazil’s state of Amazonas provides an unusual opportunity to quantify these impacts with clear “before” and “after” periods. Inaugurated in 2011, the bridge connects Manaus to forest areas on the right bank of the river, thus opening a new frontier for peri-urban expansion. We used the AGROECO model in the Dinamica-EGO software to simulate “Bridge” and “No-bridge” scenarios to evaluate the spatial dynamics of deforestation in the municipalities (counties) of Iranduba, Manacapuru and Novo Airão. Simulated deforestation between 2011 and 2030 for the study area as a whole was 106% higher with the bridge. The portion of the study area with expansion of roads had four times more deforestation in the Bridge scenario than in the No-bridge scenario. A change in the spatial distribution of the deforested area was detected, with an advance of deforestation in the municipality closest to the bridge. Deforestation also expanded in more distant regions. Peri-urbanization in the Bridge scenario demonstrates the possible increase in the spatial distribution of deforestation activity beyond the already-consolidated frontier, making the deforestation pattern more diffuse and leaving the remaining forest even more vulnerable. Impact of the bridge could further increase due to additional factors, such as the planned opening of a highway (BR-319) connecting Manaus to Brazil’s “arc of deforestation.” HighlightsCompletion of Brazil’s Rio Negro Bridge in Manaus in 2011 allows urban expansion.Simulated deforestation to 2030 in the area accessed is 106% higher with the bridge.Clearing on the Rio Negro’s right bank is more spatially dispersed with the bridge.A planned highway link to the arc of deforestation could further accelerate clearing.