| 1. |
- Barrientos, Natalia, 1985-
(författare)
-
Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios : Implications for bottom water palaeothermometry
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (Elphidium clavatum, Nonionella labradorica, Cassidulina neoteretis, Oridorsalis tener, Cibicidoides wuellerstorfi and Quinqueloculina arctica). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for E. clavatum, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker Oden to the East Siberian Arctic Ocean.
|
|
| 2. |
- Klopotek, Grzegorz, 1990
(författare)
-
Observations of Artificial Radio Sources within the Framework of Geodetic Very Long Baseline Interferometry
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Very long baseline interferometry (VLBI) is a mature and fascinating technique with unique and indisputable applications in radio astronomy, planetary sciences, and space geodesy. The latter discipline is a field of science facilitating our understanding of various global-scale phenomena connected to Earth dynamics. Space geodesy provides, in the microwave regime, accurate and long-term stable celestial and terrestrial reference frames, to which those environmental changes can be properly referenced and their spatio-temporal variability can be subsequently accurately investigated. In order to attain better knowledge on complex, and yet subtle, geodynamical phenomena of scientific and economic importance, there is a need for an improved global geodetic infrastructure and enhanced quality of space-geodetic measurements. The common effort of the geodetic community known as the Global Geodetic Observing System (GGOS) shall address that need and provide the highest possible accuracy of geodetic products and reference frames as well as the high consistency across space-geodetic techniques. The ambitious goals of GGOS necessitate appropriate changes to be made also in the area of geodetic/astrometric VLBI, realized at preset in the form of the VLBI Global Observing System (VGOS), a next-generation system aiming to meet the requirements of GGOS and deliver geodetic products with an unprecedented quality. In order to make VGOS succeed, the key components of this complex system need to be refined, including also new observing concepts and scheduling strategies, in order to fully exploit the enhanced performance that this system can bring. Thanks to its characteristics, VGOS creates also a great opportunity for extending the current VLBI research with new applications, for the benefit of the scientific community and society at large. The subject of this thesis concerns observations of artificial radio sources within the framework of geodetic VLBI, in connection to both the current VLBI system and VGOS. This includes information on the combination of observations of natural radio sources and satellite/lunar objects as well as benefits and challenges related to the observing strategy and the technical feasibility of the presented concept. The thesis is based mostly on extensive simulation studies concerning objects on the Moon and geodetic Earth-orbiting satellites, but it also includes an analysis of VLBI observations of the lunar lander performed during dedicated experiments and with a global network of radio telescopes. The information content of this thesis may be treated as a further step towards global observations of artificial radio sources with VLBI in the VGOS era and stimulate new observing concepts for space geodesy.
|
|
| 3. |
- Sopher, Daniel
(författare)
-
Characterization of the structure, stratigraphy and CO2 storage potential of the Swedish sector of the Baltic and Hanö Bay basins using seismic reflection methods
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An extensive multi-channel seismic dataset acquired between 1970 and 1990 by Oljeprospektering AB (OPAB) has recently been made available by the Geological Survey of Sweden (SGU). This thesis summarizes four papers, which utilize this largely unpublished dataset to improve our understanding of the geology and CO2 storage capacity of the Baltic and Hanö Bay basins in southern Sweden.A range of new processing workflows were developed, which typically provide an improvement in the final stacked seismic image, when compared to the result obtained with the original processing. A method was developed to convert scanned images of seismic sections into SEGY files, which allows large amounts of the OPAB dataset to be imported and interpreted using modern software. A new method for joint imaging of multiples and primaries was developed, which is shown to provide an improvement in signal to noise for some of the seismic lines within the OPAB dataset. For the first time, five interpreted regional seismic profiles detailing the entire sedimentary sequence within these basins, are presented. Depth structure maps detailing the Outer Hanö Bay area and the deeper parts of the Baltic Basin were also generated. Although the overall structure and stratigraphy of the basins inferred from the reprocessed OPAB dataset are consistent with previous studies, some new observations have been made, which improve the understanding of the tectonic history of these basins and provide insight into how the depositional environments have changed throughout time. The effective CO2 storage potential within structural and stratigraphic traps is assessed for the Cambrian Viklau, När and Faludden sandstone reservoirs. A probabilistic methodology is utilized, which allows a robust assessment of the storage capacity as well as the associated uncertainty. The most favourable storage option in the Swedish sector of the Baltic Basin is assessed to be the Faludden stratigraphic trap, which is estimated to have a mid case (P50) storage capacity of 3390 Mt in the deeper part of the basin, where CO2 can be stored in a supercritical phase.
|
|
| 4. |
- Arellano, Santiago, 1981
(författare)
-
Studies of Volcanic Plumes with Remote Spectroscopic Sensing Techniques -DOAS and FTIR measurements on volcanoes of the Network for Observation of Volcanic and Atmospheric Change-
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volcanism is a rich geodynamical process, closely linked to the origin and ongoing evolution of the lithosphere, atmosphere, hydrosphere and biosphere. Humans have benefited from the resources provided by volcanoes but also been threatened by the dangers of volcanic eruptions, which accurate prediction remains elusive. This is partly due to the inherent complexity of volcanic systems and partly because of the difficulty of conducting key observations to characterize them. In particular, since the segregation and escape of magmatic volatiles are essential mechanisms behind volcanic eruptions, monitoring the intensity and composition of the resulting emissions in the atmosphere is essential to characterize the state of volcanic activity; however, their direct measurement is not always feasible.Remote spectroscopic sensing, whereby gas species can be quantified by their spectral signatures in electromagnetic radiation gathered at a prudent distance from the plume, offers the possibility to conduct reliable and sustainable monitoring of volcanic emissions. To expand the remote sensing capabilities of volcanological observatories the Network for Observation of Volcanic and Atmospheric Change (NOVAC) was established in 2005. The central theme of this thesis is the acquisition, analysis and interpretation of measurements of volcanic gas emissions on volcanoes of NOVAC. Measurements of the mass flow rate of SO2 and the molar ratios of SO2 against BrO and HCl were obtained by scanning-Differential Optical Absorption Spectroscopy (DOAS) of scattered solar ultraviolet radiation and by Fourier-Transform Spectroscopy (FTIR) of direct solar infrared radiation. The uncertainty of the measurements is characterized and methods for combining observations from different sensors implemented. Statistical and physical models of degassing are proposed for selected volcanoes of the network. The resulting time-series of emission on 16 volcanoes is one of the more detailed compilations of volcanic degassing in the last decade, particularly from passive emissions which are difficult to detect from satellite platforms. This work aims at advancing our knowledge of volcanic eruptions for a better mitigation of their risks.
|
|
| 5. |
- Salas Romero, Silvia
(författare)
-
Multidisciplinary Near-Surface Investigation of a Quick-Clay Landslide Prone Area in Southwest Sweden
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quick-clay landslides are considered one of the most important geohazards in Sweden, Norway, and Canada. The deposits involved are glacial and postglacial clays and silty clays, which are very sensitive to increased stress that may collapse their structure and cause liquefaction.A multidisciplinary approach was adopted in this study of quick clays in an area of southwest Sweden that is prone to landslides. It was mainly based on geophysical methods, but was complemented and validated with geotechnical, geological, and hydrological data. Downhole geophysics, land and river reflection seismics, radio magnetotellurics, P-wave refraction tomography, magnetics, and multichannel analysis of surface waves comprised the main geophysical methods used in this research. Laboratory measurements of core samples, such as grain size analysis, mineral magnetic properties, fossil content, X-ray fluorescence, cation exchange capacity, X-ray powder diffraction, electrical conductivity, and pH were also taken. Hydrological modelling was used to obtain information on the properties of groundwater within a coarse-grained layer, given the importance of this information in the formation of quick clays.The evaluation of the physico-chemical properties of the coarse-grained layer revealed high values of magnetic susceptibility, probably as a result of fluvial sorting, which tends to accumulate denser minerals such as magnetite. Potential quick clays were visually observed above this layer, and their presence was also confirmed by geotechnical data acquired in previous studies. Marine fossils identified within the coarse-grained layer confirmed the glaciomarine origin of the clays. Geophysical results revealed the presence of large-scale structures, an undulating fractured bedrock and a coarse-grained layer sandwiched between clay deposits, with leached sediments on top and unleached sediments below. This layer, important for the development of quick clays in the area, was 3D modelled in a regional context. Magnetic data also revealed that the coarse-grained layer together with quick clays, have the potential to act as a sliding prone layer. Multichannel analysis of surface waves helped to geotechnically characterize the area. Although the results could not reach the deeper layers, it did yield information about the shallower layers of clay, silt and sand. The VS30 values indicated the presence of soft soils, as well as soft clays/silts with high plasticity index and high water content.This PhD is expected to improve the current knowledge of quick-clay landslides and how they are preconditioned. Climate change will probably affect the study area in the near future, most likely increasing landslide risk, therefore, research should continue and advance to new levels. Application of other geophysical methods such as borehole or geophysical monitoring, and induced polarization, could provide more information about the formation of quick clays and associated landslides.
|
|
| 6. |
- Bernhardson, Martin
(författare)
-
Aeolian dunes of central Sweden
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.The shape and orientation of a dune is determined by the local environment during its formation, such as the abundance of sediment available for entrainment by the wind, groundwater table fluctuations, changes to precipitation and temperature, presence/absence of vegetation, mode of the wind et cetera. By determining the type of dunes it is possible to determine the local environment during their formation. If one also can determine when these dunes formed and stabilised one can determine the palaeoenvironment, and in extension the palaeoclimate, during a specific time period.In this thesis, new findings are presented regarding the geomorphology, geochronology and palaeoenvironment of a number of dunes and dune fields in south and central Sweden, based on state-of-the-art methods, such as LiDAR (light detection and ranging) based remote sensing and optically stimulated luminescence dating. The previous hypotheses concerning the formation of these dunes have also been evaluated.The findings show that the dunes of central Sweden are primarily of a transverse type, i.e. their dune ridges are transverse to the dune forming winds and they were formed in a setting devoid of vegetation and with an abundance of sediment. The primary dune forming winds for these transverse dunes appear to have been north-westerly and westerly winds. The investigated dunes further to the south show signs of having been reworked after their initial formation and are often of a parabolic type, i.e. curved/crescentic in shape with their arms facing upwind. These dunes have been described as strongly linked to the presence of vegetation, and can often be considered secondary dune forms. These more southern dunes appear to also mainly have been formed by north-westerly and westerly winds, although they display a bigger scatter in wind directions than the more northern dunes.The luminescence ages suggest that most of the dunes formed during the early Holocene, and later events of sand drift have been uncommon with only minor impact on the dune morphology. There seems to have been a primary dune stabilisation phase ~10-9 ka, irrespective of the latitude of the dune fields. This means that some dune fields formed close after local deglaciation, while others formed millennia later. This suggests that dune formation and dune stabilisation of central Sweden have been controlled by regional environmental conditions. Extremely low lake levels in southern and south-central Sweden 10.5-9.5 ka BP in conjunction with an unstable climate during early Holocene probably delayed dune stabilisation by vegetation. After the vegetation had stabilised the dunes, they became much more resilient to further fluctuations in the climate.
|
|
| 7. |
- Hossain, Mohammed, 1960-
(författare)
-
Sustainable Arsenic Mitigation A Strategy for Scaling-up Safe Water Access : A Strategy for Scaling-up Safe Water Access
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In rural Bangladesh, the drinking water supply is mostly dependent upon manually operated hand pumped tubewells, installed by the local community. The presence of natural arsenic (As) in groundwater and its wide scale occurrence has drastically reduced the safe water access across the country and put tens of millions of people under health risk. Despite significant progress in understanding the source and distribution of As and its mobilization through sediment-water interactions, there has been limited success in mitigation since the problem was discovered in the country’s water supply in 1993. This study evaluated the viability of other kinds of alternative safe drinking water options and found tubewells are the most suitable due to simplicity and technical suitability, a wide acceptance by society and above all low cost for installation, operation and maintenance. During planning and decision making in the process of tubewell installation, depth of the tubewell is a key parameter as it is related to groundwater quality and cost of installation. The shallow wells (usually < 80m) are mostly at risk of As contamination. One mitigation option are deep wells drilled countrywide to depths of around 250 m. Compared to safe water demand, the number of deep wells is still very low, as the installation cost is beyond affordability of the local community, especially for the poor and disadvantaged section of the society. Using depth-specific piezometers (n=82) installed in 15 locations spread over the 410 km2 area of Matlab (an As-hot spot) in southeastern Bangladesh, groundwater monitoring was done over a 3 year period (pre- and post-monsoon for 2009-2011 period). Measurements were performed for hydrogeological characterization of shallow, intermediate deep and deep aquifer systems to determine the possibility of targeting safe aquifers at different depths as the source of a sustainable drinking water supply. In all monitoring piezometers, As was found consistently within a narrow band of oscillation probably due to seasonal effects. Hydrogeochemically, high-As shallow groundwaters derived from black sands are associated with elevated DOC, HCO3, Fe, NH4-N and PO4-P and with a relatively low concentration of Mn and SO4. Opposite to this, shallow aquifers composed of red and off-white sediments providing As-safe groundwater are associated with low DOC, HCO3, Fe, NH4-N and PO4-P and relatively higher Mn and SO4. Groundwaters sampled from intermediate deep and deep piezometers which were found to be low in As, are characterized by much lower DOC, HCO3, NH4-N and PO4-P compared to the shallow aquifers. Shallow groundwaters are mostly Ca-Mg-HCO3 type and intermediate deep and deep aquifers’ groundwaters are mostly Na-Ca-Mg-Cl-HCO3 to Na-Cl-HCO3 type.A sediment color tool was also developed on the basis of local driller’s color perception of sediments (Black, White, Off-white and Red), As concentration of tubewell waters and respective color of aquifer sediments. A total of 2240 sediment samples were collected at intervals of 1.5 m up to a depth of 100 m from all 15 nest locations. All samples were assigned with a Munsell color and code, which eventually led to identify 60 color varieties. The process continued in order to narrow the color choices to four as perceived and used by the local drillers for identification of the targeted As-safe aquifers. Munsell color codes assigned to these sediments render them distinctive from each other which reduces the risk for misinterpretation of the sediment colors. During the process of color grouping, a participatory approach was considered taking the opinions of local drillers, technicians, and geologists into account. In addition to the monitoring wells installed in the piezometer nests, results from 87 other existing drinking water supply tubewells were also considered for this study. A total of 39 wells installed in red sands at shallow depths producing As-safe water providing strong evidence that red sediments are associated with As-safe water. Average and median values were found to be less than the WHO guideline value of 10 μg/L. Observations for off-white sediments were also quite similar. Targeting off-white sands could be limited due to uncertainty of proper identification of color, specifically when day-light is a factor. Elevated Mn in red and off-white sands is a concern in the safe water issue and emphasizes the necessity of a better understanding of the health impact of Mn. White sediments in shallow aquifers are relatively uncommon and seemed to be less important for well installations. Arsenic concentrations in more than 90% of the shallow wells installed in black sands are high with an average of 239 μg/L from 66 wells installed in black sediments. It is thereby recommended that black sands in shallow aquifers must be avoided. This sediment color tool shows the potential for enhancing the ability of local tubewell drillers for the installation of As-safe shallow drinking water tubewells.Considering the long-term goal of the drinking water safety plan to provide As-safe and low-Mn drinking water supply, this study also pioneered hydrogeological exploration of the intermediate deep aquifer (IDA) through drilling up to a depth of 120 m. Clusters of tubewells installed through site optimization around the monitoring piezometer showed a similar hydrochemical buffer and proved IDA as a potential source for As-safe and low-Mn groundwater. Bangladesh drinking water standard for As (50 µg/L) was exceeded in only 3 wells (1%) and 240 wells (99%) were found to be safe. More than 91% (n=222) of the wells were found to comply with the WHO guideline value of 10 µg/L. For Mn, 89% (n=217) of the wells show the concentration within or below the previous WHO guideline value of 0.4 mg/L, with a mean and median value of 0.18 and 0.07 mg/L respectively. The aquifer explored in the Matlab area shows a clear pattern of low As and low Mn. The availability of similar sand aquifers elsewhere at this depth range could be a new horizon for tapping safe drinking water at about half the cost of deep tubewell installation.All findings made this study a comprehensive approach and strategy for replication towards As mitigation and scaling-up safe water access in other areas of Bangladesh and elsewhere having a similar hydrogeological environment.
|
|
| 8. |
- Linkhorst, Annika
(författare)
-
Greenhouse gas emission from tropical reservoirs : Spatial and temporal dynamics
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The emission of methane (CH4) and carbon dioxide (CO2) from reservoirs has been estimated to make up for about 1.3% of the global anthropogenic greenhouse gas emission. The impoundment of a river leads to the accumulation of sediment that is brought in from inflowing rivers, and the sediment organic matter is degraded to CH4 and CO2. CH4 is of particular concern as its global warming potential is 34 times stronger than that of CO2. In the tropics, high temperatures and high availability of fresh organic matter from high net primary production fuel CH4 and CO2 production. As the construction of hydropower plants is currently undergoing a boom, especially in the tropics, reservoir emission is probably bound to increase.The emission of CH4 and CO2 from reservoir surfaces is, however, highly variable, which makes current estimates uncertain. This thesis is built on the hypothesis that the spatial and temporal variability of greenhouse gas emission in tropical reservoirs, particularly of CH4 ebullition (the emission via gas bubbles), is so large that the sampling strategy affects whole-system estimates of greenhouse gas emission.This thesis shows that greenhouse gas emission from the four studied tropical reservoirs in Brazil varied greatly at different timescales – over 24 hours, between days and between seasons. Seasonal variability was identified as the most important temporal scale to be covered for CH4 ebullition inventories. In addition, the spatial variability of gas emission was large for all pathways. The variability of CH4 ebullition across space, for example, was estimated to be almost as large as its variability between seasons, and patterns of spatial variability in diffusive CH4 and CO2 emission differed between seasons. For both ebullition and diffusion, river inflow areas were prone to elevated greenhouse gas emission.This thesis shows that for retrieving solid emission estimates, there is no alternative to time-consuming measurements in the field. Measurements should be repeated at least once during each hydrological season (i.e. falling and rising water level). The seasonal surveys should cover space at a high resolution, including areas with and without river inflows, and different water column depths. CH4 ebullition made up for 60–99% of the total CO2-equivalent emission from the whole water surface of the studied reservoirs, with the highest contribution in the most productive reservoir. The most variable greenhouse gas emission pathway is therefore the most important one to be measured at appropriate resolution, particularly in productive reservoirs.
|
|
| 9. |
- Acosta Navarro, Juan Camilo, 1983-
(författare)
-
Anthropogenic influence on climate through changes in aerosol emissions from air pollution and land use change
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Particulate matter suspended in air (i.e. aerosol particles) exerts a substantial influence on the climate of our planet and is responsible for causing severe public health problems in many regions across the globe. Human activities have altered the natural and anthropogenic emissions of aerosol particles through direct emissions or indirectly by modifying natural sources. The climate effects of the latter have been largely overlooked. Humans have dramatically altered the land surface of the planet causing changes in natural aerosol emissions from vegetated areas. Regulation on anthropogenic and natural aerosol emissions have the potential to affect the climate on regional to global scales. Furthermore, the regional climate effects of aerosol particles could potentially be very different than the ones caused by other climate forcers (e.g. well mixed greenhouse gases). The main objective of this work was to investigate the climatic effects of land use and air pollution via aerosol changes.Using numerical model simulations it was found that land use changes in the past millennium have likely caused a positive radiative forcing via aerosol climate interactions. The forcing is an order of magnitude smaller and has an opposite sign than the radiative forcing caused by direct aerosol emissions changes from other human activities. The results also indicate that future reductions of fossil fuel aerosols via air quality regulations may lead to an additional warming of the planet by mid-21st century and could also cause an important Arctic amplification of the warming. In addition, the mean position of the intertropical convergence zone and the Asian monsoon appear to be sensitive to aerosol emission reductions from air quality regulations. For these reasons, climate mitigation policies should take into consideration aerosol air pollution, which has not received sufficient attention in the past.
|
|
| 10. |
- Pendrill, Florence, 1983
(författare)
-
Where have all the forests gone? Quantifying pantropical deforestation drivers
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deforestation across the tropics continues to be a major source of greenhouse gas emissions and the largest threat to biodiversity on land. With strengthened commitments to reduce deforestation from countries and companies alike, it is crucial that renewed investments for reducing deforestation be guided by a sound understanding of what drives deforestation. This thesis gives a comprehensive picture of the amount of deforestation and concomitant carbon emissions driven by the expansion of agricultural commodities across the tropics and its link to international trade. The included papers show that pasture and a handful of crops drive a large share of the deforestation resulting in the expansion of productive agriculture. The main demand for these commodities is domestic consumption; even so, imports of food commodities associated with deforestation can still constitute a large part of the consumer countries’ carbon emissions due to consumption (e.g., in the EU). This thesis contributes empirical evidence relating to forest transition theories by showing that many countries with increasing forest cover tend to import products associated with deforestation elsewhere, thereby offsetting around one-third of their forest gains. The thesis also introduces a conceptual distinction between two categories of agriculture-driven deforestation, based on whether it results in productive agricultural land or not. Though almost all deforestation is agriculture-driven, one-third to one-half of agriculture-driven deforestation occurs without the expansion of productive agricultural land. Instead, it may be due to several potential mechanisms, such as land speculation, tenure issues, or fires. Put together, these results indicate that it is crucial that policies to curb deforestation go beyond focusing only on trade in specific commodities, to help foster concerted action on rural development, territorial governance, and land-use planning. This thesis also highlights key evidence gaps on the links between deforestation and agriculture: (i) the attribution of deforestation to specific commodities currently often relies on coarse or outdated data, (ii) there is a need for improved data on deforestation trends, and (iii) our understanding of deforestation drivers is systematically poorer for dry forests and Africa.
|
|
