<p>Tropical ecosystems play a key role in regulating the global climate and the carbon cycle thanks to the large amounts of water and carbon exchanged with the atmosphere. These biogeochemical fluxes are largely the result of high photosynthetic rates. Photosynthetic activity is highly dependent on climate and vegetation, and therefore can be easily modified along with changes in those two factors. A better understanding of what drives or alters photosynthetic activity in the tropics will lead to more accurate predictions of climate and subsequent effects on ecosystems. The seasonal pattern of photosynthetic activity is one of the main uncertainties that we still have about tropical ecosystems. However, this seasonality of tropical vegetation and its relationship to climate change and land cover is key to understanding how these ecosystems could be affected and have an effect on climate.</p><p>In this dissertation, I present three projects to improve our understanding about tropical ecosystems and how their photosynthetic activity is affected by climate and land cover change. The lack of field-based data has been one of the main limiting factors in our study of tropical ecosystems. Therefore, in these projects I extensively use remote sensing-derived data to analyze large scale and long term patterns. In the first study, I looked at the seasonal relationship between photosynthetic activity and climate, and how model simulations represent it. Vegetation in most of the tropics is either positively correlated with both water and light, or positively correlated with one of them and negatively with the other. Ecosystem models largely underestimate positive correlations with light and overestimate positive correlations with water. In the second study, I focus on the effect of land cover change in photosynthetic activity and transpiration in a highly deforested region in the Amazon. I find that land cover change decreases tropical forests photosynthetic activity and transpiration during the dry season. Also, land cover change increases the range of photosynthetic activity and transpiration in forests and shrublands. These effects are intensified with increasing land cover change. In the last project, I quantify the amount of change in evapotranspiration due to land cover change in the entire Amazon basin. Our remote sensing-derived estimates are well aligned with model predictions published in the past three decades. These results increase our confidence in climate models representation of evapotranspiration in the Amazon.</p><p>Findings from this dissertation highlight (1) the importance of the close relationship between climate and photosynthetic activity and (2) how land cover change is altering that relationship. We hope our results can build on our knowledge about tropical ecosystems and how they could change in the future. We also expect our analysis to be used for model benchmarking and tropical ecosystem monitoring.</p>

Mozambique is to fifty percent covered by forest, most of which belongs to the biodiverse miombo woodlands. The last decades, Mozambique has been suffering from rapid deforestation. The once continuous forest cover has turned into a mosaic of forest patches, farmland, settlements etc. The remaining forest patches are in many cases very isolated. These forests have distinct edges towards the neighbouring land, which means that the edge zones have different environmental conditions (more light, higher temperatures etc.) and tree species composition than the interior. In order to examine how the forests of Mozambique are affected by edge effects, the highly isolated Nhamacoa forest was studied. An additional aim of the project was to make a floristic inventory of the forest in order to further assess its conservation status. Specimens were collected, pressed and photographed for identification. Edge effects were studied in plots at the edge and in the interior of the forest in a paired design. Trees inside the plots were identified, counted and measured (dbh (diameter at breast height) and height) to search for differences in species richness, diversity, biomass and height-to-dbh ratios. Environmental parameters (air temp., soil temp., light and slope) were also measured. In total, 76 species of trees were sampled and 44 (35 in the interior and 32 at the edge) of these were found inside the plots. The interior plots harboured significantly more individuals and species of trees than their paired edge plots. Additionally, biomass and height-to-dbh ratios were higher in the interior plots than in the edge plots. These differences strongly suggest that the Nhamacoa forest is affected by edge effects, although none of the measured environmental parameters could explain why. That the Nhamacoa forest is affected by edge effects goes in line with the research hypothesis and shows that it is important to maintain large and intact pieces of forest in order to preserve the Mozambican miombo forests. For future studies, additional environmental parameters (wind speed, humidity etc.) could be examined in order to better explain the presence of edge effects in the Nhamacoa forest.

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No description available.

<p>This research explores the impact of road infrastructure on deforestation, the role of forest governance and a carbon tax/credit mechanism in mitigating the effect on land use change and subsequent GHG emissions, with application to the states of Pará and Mato Grosso in Brazil. Few studies have addressed how policies to protect forested land affect the rate of deforestation associated with road and infrastructure improvement. This research makes three main contributions to the literature of roads and deforestation: 1) the concept of cost of access to the “closest” market in terms of time (expressed in person hours per ten ton load) is introduced to reflect variations in the road network infrastructure; 2) development of empirical evidence of the role of forest governance in diminishing the rate of deforestation linked to roads, using data from Brazil; and 3) and assessment of the efficacy of a carbon tax/credit scheme for mitigating the impact of infrastructure investment on land use and resultant changes in GHG emissions. Access cost ranged between 0.01 and 3084 person hours per load, however 80 percent of the pixels measured less than 784 person hours across the three years analyzed (2003, 2013, and 2018). This measure facilitated a contrast in spatial accessibility due to road infrastructure across pixels within the same year and across years on a same pixel. The use of a fractional logit model allowed the incorporation of proportions of different land uses within a same pixel at the same resolution of other <a></a>variables not available at the same fine scale. Strong forest governance reduced up to 25% the elasticities on forest lands with respect to access cost; in other words, the impact of roads on deforestation is reduced by one fourth when forest governance is strengthened. These larger impacts occur at the frontier where most of the efforts need to be addressed. Finally, provided a shock in road infrastructure, a carbon tax/credit level of $82/tCO2e permitted to abate an additional amount of GHG emissions estimated in 244 million tons of CO2e released due to changes in carbon stocks and flow emissions from agricultural activities induced from changes in road infrastructure. More importantly, this research provided insights of a proportion of GHG emissions that could be abated at different levels of a carbon tax/credit.</p>

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Legal Amazon, the Brazilian region where much of the global tropical forest is located, has suffered from rapid deforestation for decades, undermining the provision of ecosystem services and the conservation of biodiversity on local and global scales. In order to prevent deforestation, the Brazilian government has established priority and protected areas to ensure the preservation of high biodiversity areas and ecosystem services. This study analyses whether the establishment of priority and protected areas have an impact in preventing deforestation, thus promoting biodiversity and ecosystem services. Furthermore, this study also analyses the extent to which deforestation affects priority areas for biodiversity conservation. Deforestation datasets from 2001 to 2014 of the Legal Amazon was processed and analyzed. The total area and density of deforestation were compared across three categories of land: (1) protected priority areas, (2) unprotected priority areas, and (3) non-priority areas. Spatial methods of geoprocessing and the statistical method one-way ANOVA were used to analyse the deforestation trends. As a result, the deforestation density was found to be lowest inside protected areas than in unprotected areas and non-priority areas. This implied that land-use restrictions in protected areas had more impact compared to unprotected areas and non-priority areas. Furthermore, deforestation has been more intensive in regions of lower biodiversity importance. Despite this positive evaluation, substantial tracts of forest had been converted within regions of high biodiversity importance. Therefore, the regulation of priority and protected areas must be evaluated and improved in the future. / Den brasilianska regionen Legal Amazon, där mycket av den globala andelen av tropisk skog ligger, har drabbats av snabb avskogning i årtionden, vilket underminerar tillhandahållandet av ekosystemtjänster och bevarandet av den biologiska mångfalden både på lokal och global skala. För att förhindra avskogning har den brasilianska regeringen etablerat prioriterade och skyddade områden för att säkerställa bevarandet av områden med hög biologisk mångfald och ekosystemtjänster. Denna studie analyserar huruvida etableringen av prioriterade och skyddade områden påverkar förebyggandet av denna avskogning. Dessutom analyserar denna undersökning också hur omfattningen av avskogningen påverkar prioriterade områden för bevarande av biologisk mångfald. Avskogningsdata från 2001 till 2014 i Legal Amazon bearbetades och analyserades. Total areal och densitet av avskogningen jämfördes mellan tre kategorier av mark: (1) skyddade prioriterade områden, (2) oskyddade prioriterade områden och (3) icke prioriterade områden. Rumsliga metoder för bearbetning och den statistiska metoden envägs-ANOVA användes för att analysera avskogningstrenderna. Resultaten visar att avskogningstätheten var lägst inom skyddade områden jämfört med oskyddade områden och icke-prioriterade områden. Det innebär att markanvändningsbegränsningar i skyddade områden har haft större inverkan jämfört med oskyddade områden och icke prioriterade områden. Vidare har avskogningen varit mer intensiv i områden med lägre värden för biologisk mångfald. Trots denna positiva utvärdering hade ett betydande skogsområde omvandlats inom områden med höga värden för biologisk mångfald. Därför måste regleringen av prioriterade och skyddade områden utvärderas och förbättras i framtiden.

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[pt] O sistema alimentar global que conhecemos não consegue prover a segurança alimentar para todos. A regulamentação não é suficiente para garantir o acesso econômico a alimentos pela população. Somadas as pressões de crescimento populacional até 2050, a disponibilidade de alimentos pela expansão da produção é uma questão-chave. O Brasil é um país central por ser um grande produtor e exportador de alimentos e insumos e possuir terras e água que subsidie a expansão. Entretanto, a produção de alimentos gera muitas externalidades. As ações de prevenção e mitigação das externalidades negativas ambientais são fundamentais, especialmente nos países onde a produção ocorre. A contínua disponibilização de alimentos e o próprio setor agropecuário dependem do meio ambiente para se reproduzir no tempo. Este trabalho analisa os mecanismos de planejamento e avaliação existentes no Brasil de modo a garantir que as externalidades diretas e indiretas do desmatamento para produção de alimentos sejam tratadas. Entende-se, ao fim, que apesar da diversidade e número de mecanismos, estes não possuem a escala, complexidade e integração necessárias para o ordenamento da contínua produção de carne bovina e soja no Brasil até 2050 e da proteção dos biomas. Os mecanismos não consideraram as externalidades diretas e indiretas do desmatamento de modo satisfatório. Recomenda-se integrar indicadores das externalidades diretas e indiretas do desmatamento nos mecanismos de avaliação e planejamento; que crie se e faça cumprir o Zoneamento Econômico Ecológico no Brasil incluindo zonas de não desmatamento; e que se estabeleça um Fórum multi-setorial para criar as condições de governança necessárias para realização das recomendações anteriores. / [en] The current global food system cannot provide food security for all. Its regulatory framework is not enough to guarantee economic access to food to all people. This coupled with the pressures of population growth up to 2050 puts the availability of food as key issue. Brazil is a key country on this issue country for being a major producer and exporter of food and inputs, and owning land and water to subsidize expansion. However, food production generates many externalities. Actions to prevent and mitigate negative environmental externalities are critical, especially in countries where production occurs. The continuous availability of food and the agricultural sector itself depend on the environment for reproduction over time. This thesis analyzes the existing planning and evaluation mechanisms in Brazil to ensure that the direct and indirect externalities of deforestation for food production are addressed. In the end, it is understood that despite the diversity and number of mechanisms, these do not have the scale, complexity and integration needed for territorial organization of the continuous production of beef and soybeans in Brazil up to 2050 and the protection of biomes. The analyzed mechanisms did not consider the direct externalities of deforestation in a satisfactory way. Recommendations are: to integrate indicators of the direct and indirect externalities of deforestation in evaluation and planning mechanisms; to create and enforce the Ecological Economic Zoning in Brazil including zones of no deforestation; and that a multi-sectoral Forum be established to create governance conditions for the implementation of the previous recommendations.