Achim Röder

• PhD
• Trier University

This study introduces a novel approach for mapping annual fractional vegetation cover in Sub-Saharan range-lands. We used Sentinel-2 time series data from October 2022 to October 2023 to derive phenological metrics, including the dry season integral and rate of greenness decline after peak season. Phenological metrics effectively separate woody veg...

Land use is a key driver of the ongoing biodiversity crisis and therefore also a major opportunity for its miti-gation. However, appropriately considering the diversity of land-use actors and activities in conservation assessments and planning is challenging. As a result, top-down conservation policy and planning are often criticized for a lack of...

Dry savannahs are highly sensitive to climate change and under intense anthropogenic pressure. Therefore, the methods for assessing their status should be easy and repeatable. Monitoring through satellite data and field measurements are limited in accurately assessing the spatiotemporal dynamics of ecosystems. Fortunately, emerging technologies lik...

We present a framework for mapping grazing management units in extensive pastoral landscapes. Mapping such units from remote sensing, particularly in the pastoral landscapes of East Africa, is usually hampered by high cost of field data collection and by the fact that the relationship between rangeland ecological characteristics and rangeland use f...

Open and analysis-ready data, as well as methodological and technical advancements have resulted in an unprecedented capability for observing the Earth’s land surfaces. Over 10 years ago, Landsat time series analyses were inevitably limited to a few expensive images from carefully selected acquisition dates. Yet, such a static selection may have in...

The process of land degradation needs to be understood at various spatial and temporal scales in order to protect ecosystem services and communities directly dependent on it. This is especially true for regions in sub-Saharan Africa, where socio economic and political factors exacerbate ecological degradation. This study identifies spatially explic...

This study aimed to map the status of mangrove forests over the coasts of Hai Ha District and Mong Cai City in Quang Ninh Province by using 2019 Landsat-8 imagery. It then developed the AGB estimation model of mangrove forests based on the AGB estimation-derived plots inventory and vegetation indices-derived from Landsat-8 data. As results, there w...

Hedgerows are one of the few remaining natural landscape features within European agricultural areas. To facilitate hedgerow monitoring, cost-effective and accurate mapping of hedgerows across large spatial scales is required. Current methods used for automatic hedgerow detection are overly complicated and generalize poorly to larger areas. We exam...

Hedgerows are one of the few remaining natural landscape features within European agricultural areas. To facilitate hedgerow monitoring, cost-effective and accurate mapping of hedgerows across large spatial scales is required. Current methods used for automatic hedgerow detection are overly complicated and generalize poorly to larger areas. We exam...

Within the Miombo belt the tri-national Okavango Basin is one of the last remaining intact river basins in Africa. It supports highly diverse social-ecological systems with the majority of the population strongly depending on the direct provision of multiple ecosystem services. Following independence and peace treaties the region is now rapidly bei...

Brazil, home to one of the planet’s last great forests, is currently in trade negotiations with its second largest trading partner, the European Union (EU). We urge the EU to seize this critical opportunity to ensure that Brazil protects human rights and the environment. Brazil’s forests, wetlands, and savannas are crucial to a great diversity of I...

Earth observation derived land surface phenology (LSP) provides important information on status and dynamics of land cover. Commonly, LSP metrics are derived from coarse resolution sensors due to their high temporal repetition rate. The coarse spatial resolution is often not sufficient of tracking land cover and its change in spatially heterogeneou...

The spatial extension of the countries covered by SASSCAL, the diversity of their landscapes, and the range of social and ecological processes, constitute a challenge to environmental research. The latter have sometimes needed to focus on small test sites for very specific questions, or else required data and methods that allowed large area assessm...

Dry tropical forests are facing large-scale conversion and degradation processes and are the most endangered forest type worldwide. We analyse these processes in the dry tropical forest type of miombo woodlands in a rural area of south-central Angola. We show that large-scale conversion to agricultural areas takes place in this area, as does modifi...

Oti-Keran-Mandouri (OKM) is part of the elephant historical range and one of the priority corridors proposed for elephant conservation in West Africa. However, its potentialities to be a functional corridor are yet to be evaluated in a context of increasing anthropogenic pressure. This study aims at assessing habitat biophysical patterns and fragme...

In southern African drylands, an important driver of deforestation is the ongoing conversion of woodland to smallholder agriculture. Our study in NE Namibia and SW Zambia evaluated the potential of operational earth observation satellites to characterize land-use change processes and quantifi ed their impact on soil organic carbon (SOC) and nutrien...

Dry tropical forests undergo massive conversion and degradation processes. This also holds true for the extensive Miombo forests that cover large parts of Southern Africa. While the largest proportional area can be found in Angola, the country still struggles with food shortages, insufficient medical and educational supplies, as well as the ongoing...

Tropical dry forests provide globally important ecosystem services and host exceptionally high biodiversity. These biomes are currently under immense pressure, particularly for conversion to agriculture, and already experience high global deforestation rates. Miombo forests in Southern Angola are affected by deforestation, fragmentation and degrada...

The need for operational monitoring of landscape processes on the national to global scale led to an increased demand for pixel-based composites using complete earth observation (EO) archives. Commonly, composites are generated without explicit consideration of temporal criteria but are rather based on optimizing band indices within a pre-defined t...

Fire spread information on a large scale is still a missing key layer for a complete description of fire regimes. We developed a novel multilevel object-based methodology that extracts valuable information about fire dynamics from Moderate Resolution Imaging Spectroradiometer (MODIS) burned area data. Besides the large area capabilities, this appro...

Satellite-derived land surface phenology (LSP) serves as a valuable input source for many environmental applications such as land cover classifications and global change studies. Commonly, LSP is derived from coarse-resolution (CR) sensors due to their well-suited temporal resolution. However, LSP is increasingly demanded at medium resolution (MR),...

The repopulation of abandoned areas in Angola after 27years of civil war led to a fast and extensive expansion of agricultural fields to meet the rising food demand. Yet, the increase in crop production at the expense of natural resources carries an inherent potential for conflicts since the demand for timber and wood extraction are also supposed t...

Spatio-temporal information on process-based forest loss is essential for a wide range of applications. Despite remote sensing being the only feasible means of monitoring forest change at regional or greater scales, there is no retrospectively available remote sensor that meets the demand of monitoring forests with the required spatial detail and g...

We developed a large-area preprocessing framework for multisensor Landsat data, capable of processing large data volumes. Cloud and cloud shadow detection is performed by a modified Fmask code. Surface reflectance is inferred from Tanré's formulation of the radiative transfer, including adjacency effect correction. A precompiled MODIS water vapor d...

We developed a spatio-temporal path reflectance climatology for use in atmospheric corrections for a Landsat pre-processing framework. The climatology is intended as a fallback strategy for aerosol estimation in bright Southern African savannah ecosys-tems where the rarity of dark objects decreases the applicability of common image-based aerosol es...

Durante um período de cinco anos (setembro de 2010 a agosto de 2015), 140 pesquisadores de oito países, 23 universidades e instituições de pesquisa adicionais, principalmente de Angola, Botsuana, Namíbia e Alemanha, realizaram o projeto de pesquisa transdisciplinar ‚The Future Okavango‘ (TFO) dentro de toda a Bacia do Okavango-Cubango. Este livro é...

We developed a new two-step approach for automated masking of clouds and their shadows in Landsat imagery. The first step consists of detecting clouds and cloud shadows in every Landsat image independently by using the Fmask algorithm. We modified two features of the original Fmask: we dropped the termination criterion for shadow matching, and we a...

The Okavango catchment is a hot spot of accelerating land use change. In particular, climate predictions, demographic developments and a growing utilization of ecosystem services and functions are expected to increase pressure on resources and land. Land use conflicts, the sustenance of precarious livelihoods, deforestation of woodland savannahs, u...

Aboveground net primary productivity (ANPP) is limited by water availability especially in dry and desert regions, and many studies have linked ANPP to current and previous “effective” rainfall events. In this study a distributed lag-model (DLM) was used to assess the impact of current and previous 16day rainfall anomalies on the Enhanced Vegetatio...

This study aimed to determine the functional seasonal attributes for herbivores of the major habitats and landscapes of the Savuti-Mababe-Linyanti ecosystem (SMLE) of northern Botswana and how various herbivore species responded to this heterogeneity. Floodplain grasslands and dambo grasslands provided the only significant green forage and biomass...

The analysis and evaluation of ecosystems in the Okavango region must include a thorough analysis of the fire regime. This requires a full understanding of its components such as fire frequency, fire season and fire intensity. For the Okavango region these components were derived based on an extensive multi-scale compilation of the MODIS products “...

The repopulation of abandoned areas in Angola after the 27 years of civil war led to a fast and extensive expansion of agricultural fields to meet the rising food demand. This effect is supported by the improvement of infrastructure and has a large impact on the natural vegetation.We evaluated agricultural expansion in our study area in the south o...

The country of Spain is representative of land change processes in Mediterranean member states of the European Union (EU). These land change processes are often triggered by European, national and sub-national policies and include widespread land abandonment and urbanisation trends, as well as an increase in land use intensities accompanied by stro...

The spatial resolution of Landsat imagery has proven to be well suited for the analysis of vegetation patterns and dynamics at regional scale; however, the low temporal frequency is often a limitation for the quantification of vegetation dynamics. The spatial and temporal adaptive reflectance fusion model (STARFM) combines moderate resolution imagi...

The aim of this study was to evaluate the potentials and limits of remote sensing time series regarding change analysis of drylands. We focussed on the assessment and monitoring of land degradation using different scales of remote sensing data. Special interest was paid on how the spatial resolutions of different sensors influence the derivation of...

The county of Lagadas in northern Greece is typical for heterogeneous Mediterranean rangelands embedded within a patchwork of land use types. In front of the spatial configuration of the landscape, major changes in rural economies were experienced in past years which have caused competing demands of different stakeholders on the utilization of natu...

Rangeland ecosystems are important elements of Mediterranean landscapes and provide a variety of goods and services, ranging from resources for livestock production systems to conservation of flora and fauna. The sustainable use of areas dominated by livestock grazing requires finding the sometimes delicate balance between productivity and correspo...

Land degradation and desertification are amongst the most severe threats to human welfare and the environment, as they affect the livelihoods of some 2 billion people in the world’s drylands, and they are directly connected to pressing global environmental problems, such as the loss of biological diversity or global climate change. Strategies to co...

In past decades, the European Mediterranean has undergone widespread land use transformations. These are largely driven by changes of socio-economic conditions, such as accession to the European Community, and had strong effects on the way the land is being used. Aiming at a systematic description of such change processes on a global level, the syn...

Land degradation is caused by and has impacts on both the social and natural components of coupled human–environment systems. However, few studies integrate both aspects simultaneously. The main objective of this study is to test a method to evaluate land degradation based on the integration of aggregate metrics of biophysical and socio-economic “d...

Land use conversions or changes of land management practices are primary drivers of global environmental change. 'Natural experiment' situations, where some conditions vary, but other potential land use determinants remain relatively constant, offer unique opportunities to study land use change, its drivers and feedbacks on human-environment system...

Mediterranean rangelands are unique marginal ecosystems, which are characterized by a highly heterogeneous structure and are often interwoven with other ecosystems. Traditionally, rangelands provided resources for livestock grazing in transhumantic rotation schemes. In recent times, there has been a trend towards semi-intensive grazing systems, whi...

The Ayora region, situated about 60 km southwest of the city of Valencia/Spain, was chosen to demonstrate pathways of characterizing fire events and post-fire succession in Mediterranean ecosystems using multi-temporal satellite imagery. A corresponding time series of 6 Landsat MSS, 13 Landsat-5 TM and 1 Landsat-7 ETM + images, covering the period...

The number of large fires increased in the 1970s in the Valencia region (eastern Spain), as in most northern Mediterranean countries, owing to the fuel accumulation that affected large areas as a consequence of an intensive land abandonment. The Ayora site (Valencia province) was affected by a large fire in July 1979. We parameterised the fire grow...

Livestock grazing has been an important factor in shaping Mediterranean rangelands. Despite their long history of utilisation, recent changes in socio-economic frameworks and the intensification of grazing systems have frequently caused rangeland ecosystems to depart from equilibrium states and initiated degradation processes. Remote sensing allows...

The number of large fires increased in the 1970s in the Valencia region (eastern Spain), as in most northern Mediterranean countries, owing to the fuel accumulation that affected large areas as a consequence of an intensive land abandonment. The Ayora site (Valencia province) was affected by a large fire in July 1979. We parameterised the fire grow...

Monitoring and assessment of land degradation and the processes driving it require effective change indicators at appropriate scales and spatial extent. In this context, the decomposition of Mediterranean rangeland vegetation into woody and herbaceous fractions is of great significance. This study demonstrates that a stratification of vegetation in...

IntroductionRemote Sensing ConceptsThe Analysis of Environmental Change with Landsat SatellitesDiscussionAcknowledgements

The establishment of monitoring frameworks for environmental problems is frequently based on retrospective, multi-temporal series of satellite images. The derivation of concise conclusions from these series largely depends on their quantitative consistency; hence, a completely standardized analysis of multi-temporal time series is mandatory. In the...

Mediterrane ‚Rangelands’ bezeichnen marginale Räume, die keiner primären Nutzung unterliegen, aber wegen ihrer Bedeutung als Weideland, für die Holzgewinnung, für Wasserkreisläufe oder als Rückzugsgebiete für Flora und Fauna von ökologischer Bedeutung sind. Das Gleichgewicht mit ihrer Nutzung wird durch starke ökonomische und gesellschaftliche Verä...

For the Sardinian study area a state-transition model (STM) was developped. which presents the different landcsape states and describes the possible transitions from one to another (e.g., transition from mixed wood to shrubland after a fire event).

Although it is well known that livestock husbandry has become more prevalent in Crete, Greece, during the last two decades, it is not well understood how grazing pressure differs spatially and how it influences grazed rangelands over time. To enhance the understanding of spatio-temporal degradation processes, a 20-year time series of Landsat Themat...

The development of vegetation cover is one of the primary indicators for land degradation, stability, or regeneration in regions threatened by overgrazing. This paper addresses the problem how spatially explicit information about degradation processes in European Mediterranean rangelands can be derived from long time series of satellite data. The s...

The importance of thoroughly monitoring the state of the environment in Mediterranean ecosystems has long been recognised. With regard to the spatial extension of large areas threatened by various degradation processes it becomes obvious that terrestrial observation alone is hardly able to cope with this task. Remote sensing with air- or spaceborne...

After a long history of utilisation, large areas of Mediterranean rangelands are today affected from transitional processes that cause conflicts between past and present land uses or economic and ecological priorities. Heavy overgrazing or the accumulation of woody biomass triggered by the abandonment and undergrazing, are causing substantial manag...

Remote sensing based data are a valuable source for extracting spatially and temporally explicit information to monitor and assess regions threatened by desertification processes. Additional value can often be added through integrating remote sensing derived information with auxiliary data through a geoinformatics approach. This paper first address...

Mediterranean lands are characterized by a highly variable mosaic of different ecosystems with a long history of utilization by man. In combination with physical factors this often caused serious damage and depletion of resources. While international political organizations responded to the growing menace of desertification or – in the European con...

The weight of fire as an environmental concern significantly increased in the second half of the past century, often as a consequence of dramatic land-use changes experienced in many countries. While a variety of prevention and restoration initiatives have been taken, the difficulty to monitor their effects over long periods and for large areas has...