Laura Vang Rasmussen

Rapid response flood detection using the MSG geostationary satellite

Abstract A novel technique for the detection of flooded land using satellite data is presented. This new method takes advantage of the high temporal resolution of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard the Meteosat Second Generation (MSG) series of satellites to derive several parameters that describe the sensitivity of land surface reflectivity to variation in solar position throughout the day. Examination of these parameters can then yield information describing the nature of the surface being viewed, including the presence of water due to flooding, on a 3-day basis. An analysis of data gathered during the 2009 flooding events in West Africa shows that the presented method can detect floods of comparable size to the SEVIRI pixel resolution on a short timescale, making it a valuable tool for large scale flood mapping.

Explaining NDVI trends in northern Burkina Faso

Many studies have shown a ‘greening of the Sahel’ on the basis of analysis of time series of satellite images and this has shown to be, at least partly, explained by changes in rainfall. In northern Burkina Faso, an area stands out as anomalous in such analysis, since it is characterized by a distinct spatial pattern and strongly dominated by negative trends in Normalized Difference Vegetation Index (NDVI). The aim of the paper is to explain this distinct pattern. When studied over the period 2000–2012, using NDVI data from the MODIS sensor the spatial pattern of NDVI trends indicates that non-climatic factors are involved. By relating NDVI trends to landscape elements and land use change we demonstrate that NDVI trends in the north-western parts of the study area are mostly related to landscape elements, while this is not the case in the south-eastern parts, where rapidly changing land use, including. expansion of irrigation, plays a major role. It is inferred that a process of increased redistribution of fine soil material, water and vegetation from plateaus and slopes to valleys, possibly related to higher grazing pressure, may provide an explanation of the observed pattern of NDVI trends. Further work will focus on testing this hypothesis.

The influence of seasonal rainfall upon Sahel vegetation

Throughout the Sahelian region of Africa, vegetation growth displays substantial inter-annual variation, causing widespread concern in the region as rain-fed agriculture and pastoralism are a means of sustenance for the predominantly rural population. Previously proposed factors behind variations include changes in total yearly rainfall, land-use change and migration. But these factors are not fully explanatory. This study addresses other possible factors for variation in vegetation patterns through the analysis of the Normalized Difference Vegetation Index (NDVI) produced by satellite sensors. We focus on precipitation, but instead of looking at the total yearly amount of rainfall, the intra-annual variation is examined. Here we show that plant growth is strongly correlated with the number and frequency of days within the rainy season upon which there is no rainfall. Furthermore, we find that if the start of the growing season, or the period in which the peak growth of vegetation occurs, is especially dry then plant growth may be stunted throughout the remainder of the season. These results enable better understanding of climate dynamics in the Sahel and allow more accurate forecasting of crop yields, carbon storage and landscape changes without the need to resort to rainfall estimates that are sometimes of low accuracy. In addition, it may be possible to apply the results to other dry land regions worldwide.

Causal relations and land use transformation in the Sahel: conceptual lenses for processes, temporal totality and inertia

The paper addresses the challenge of conceptualizing and analyzing complex change processes and causal explanations in human–environment systems. To illustrate this challenge empirically, the paper takes its point of departure in the apparent paradox that the agricultural practices in the desert fringe zone of the Sahel seem to remain remarkably unchanged despite huge and accelerating changes in major driving forces such as climate variations, population pressure, policies and market access. Such partly unexpected trends suggest that novel insight is needed into the human environment interactions that shape the use of land for cultivating purposes in this region. As a background for the paper’s conceptual discussion, recent developments in the Sahelian land use system are briefly described, using documentation from empirical case studies conducted in the northernmost region of Burkina Faso over the past 20 years. Specific attention is given to presenting (a) main trends in the transformation of the land use and livelihoods, (b) the co-evolution of possible driving forces that enables and constrains conditions for change and (c) characteristic trajectories of change. Inspired by the notions of process, temporal totality and inertia, the paper suggests employing a portfolio of complementary perspectives to investigate change processes. More precisely, four different conceptual lenses to analyze human–environment interaction are proposed and examined (the land change science framework, the double exposure notion, the system dynamics (SD) approach and coupled human–environmental timelines). Specific attention is given to the potential contribution of these respective lenses to enhancing our understanding of the land SD and to uncovering important causal relations. It is concluded that these conceptual lenses, in concert, can help to put process, in the sense of a sequence of successive stages, in the centre of our understanding of change and causal relationships in human–environmental systems.

From food to pest: Conversion factors determine switches between ecosystem services and disservices.

Abstract Ecosystem research focuses on goods and services, thereby ascribing beneficial values to the ecosystems. Depending on the context, however, outputs from ecosystems can be both positive and negative. We examined how provisioning services of wild animals and plants can switch between being services and disservices. We studied agricultural communities in Laos to illustrate when and why these switches take place. Government restrictions on land use combined with economic and cultural changes have created perceptions of rodents and plants as problem species in some communities. In other communities that are maintaining shifting cultivation practices, the very same taxa were perceived as beneficial. We propose conversion factors that in a given context can determine where an individual taxon is located along a spectrum from ecosystem service to disservice, when, and for whom. We argue that the omission of disservices in ecosystem service accounts may lead governments to direct investments at inappropriate targets.

Multiple outcomes of cultivation in the Sahel: a call for a multifunctional view of farmers’ incentives

A default assumption about the Sahel is that farmers consider food provision for the family as the sole reason for cultivation. The degree to which this ‘cultivation for food’ assumption has been embedded in the scientific literature on land use changes is signified by the fact that hardly any studies have questioned it. This article suggests that the notion of ‘cultivation for food’ tends to downplay a number of additional cultivation outcomes. By employing a conceptual framework that incorporates the concept of multifunctional agriculture, which was primarily developed for analysis of agriculture in the Global North, the study explores agricultural transitions in two villages in Burkina Faso. The analysis reveals that several household types exist, and one cannot assume that food provision is and always has been the main cultivation outcome. On the contrary, it was found that households have moved away from a sole focus on food production. Households have started to value additional cultivation outcomes like fodder production, preservation of farm identity, attachment to the village and prestige, with important differentiations between the identified household types. Hence, the paper argues that researchers and policy-makers must face the reality of new agricultural transitional pathways in the Global South.

Environmental change in the Sahel: reconciling contrasting evidence and interpretations

The Sahel has been the object of intensive international research since the drought of the early 1970s. A considerable part of the research has focused on environmental change in general and land degradation, land cover change and climate change in particular. Rich and diverse insights from many different scientific disciplines about these three domains have been put forward. One intriguing feature is that an agreement on the overall trends of environmental change does not appear to emerge: questions such as whether the Sahel is greening, cropland is encroaching on rangelands, drought persists remain contested in the scientific literature, and arguments are supported by contrasting empirical evidence. The paper explores the generic reasons behind this situation in a systematic manner. We distinguish between divergences in interpretations emerging from (1) conceptualizations, definitions and choice of indicators, (2) biases, for example, related to selection of study sites, methodological choices, measurement accuracy, perceptions among interlocutors, and selection of temporal and spatial scales of analysis. The analysis of the root causes for different interpretations suggests that differences in findings could often be considered as complementary insights rather than mutually exclusive. This will have implications for the ways in which scientific results can be expected to support regional environmental policies and contribute to knowledge production.

Adaptation by stealth: climate information use in the Great Lakes region across scales

While there has been considerable focus on understanding barriers to climate information use associated with the character of climate knowledge, individuals’ negative perception of its usability and constraints of decision-contexts, less attention has been paid to understanding how different scales of decision-making influence information use. In this study, we explore how water and resource managers’ scales of decision-making and scope of decision responsibilities influence climate information use in two Great Lakes watersheds. We find that despite availability of tailored climate information, actual use of information remains low. Reasons include (a) lack of willingness to place climate on agendas because local managers perceive climate change as politically risky, (b) lack of formal mandate or authority at the city and county scale to translate climate information into on-the-ground action, (c) problems with the information itself, and (d) perceived lack of demand for climate information by those managers who have the mandate and authority to use (or help others use) climate information. Our findings suggest that (1) scientists and information brokers should produce information that meets a range of decision needs and reserve intensive tailoring efforts for decision makers who have willingness and authority to use climate information; (2) without support from higher levels of decision-making (e.g., state), it is unlikely that climate information use will accelerate significantly; and (3) the trend towards characterizing climate specific actions within a broader concept of sustainability practices, or “adaptation by stealth,” should be supported as a component of the climate adaptation repertoire.

Social-ecological outcomes of agricultural intensification

Land-use intensification in agrarian landscapes is seen as a key strategy to simultaneously feed humanity and use ecosystems sustainably, but the conditions that support positive social-ecological outcomes remain poorly documented. We address this knowledge gap by synthesizing research that analyses how agricultural intensification affects both ecosystem services and human well-being in low- and middle-income countries. Overall, we find that agricultural intensification is rarely found to lead to simultaneous positive ecosystem service and well-being outcomes. This is particularly the case when ecosystem services other than food provisioning are taken into consideration.A comprehensive review of studies about the impact of agricultural intensification on both human well-being and ecosystem services shows mixed evidence, which depends mostly on previous land use, the sort of intensification, and what specific outcomes are measured.

Satellite passive microwaves reveal recent climate-induced carbon losses in African drylands

The African continent is facing one of the driest periods in the past three decades as well as continued deforestation. These disturbances threaten vegetation carbon (C) stocks and highlight the need for improved capabilities of monitoring large-scale aboveground carbon stock dynamics. Here we use a satellite dataset based on vegetation optical depth derived from low-frequency passive microwaves (L-VOD) to quantify annual aboveground biomass-carbon changes in sub-Saharan Africa between 2010 and 2016. L-VOD is shown not to saturate over densely vegetated areas. The overall net change in drylands (53% of the land area) was −0.05 petagrams of C per year (Pg C yr−1) associated with drying trends, and a net change of −0.02 Pg C yr−1 was observed in humid areas. These trends reflect a high inter-annual variability with a very dry year in 2015 (net change, −0.69 Pg C) with about half of the gross losses occurring in drylands. This study demonstrates, first, the applicability of L-VOD to monitor the dynamics of carbon loss and gain due to weather variations, and second, the importance of the highly dynamic and vulnerable carbon pool of dryland savannahs for the global carbon balance, despite the relatively low carbon stock per unit area.Low-frequency passive microwave data (L-VOD) allow quantification of biomass change in sub-Saharan Africa between 2010 and 2016, revealing climate-induced carbon losses, particularly in drylands.