An analysis of the recent fire regimes in the Angolan catchment of the Okavango Delta, Central Africa

Background This paper presents an analysis of fire regimes in the poorly studied Angolan catchment of the Okavango Delta in Botswana. We used MODIS data to examine the frequency and seasonality of fires over 20 years (from 2000 to 2020) in three dominant vegetation types (miombo woodlands, open woodlands and grasslands, and short closed to open bushlands), and in areas where people were present, and where they were absent. Results The median fire return intervals for both open woodlands and grasslands and short bushlands were relatively short (1.9 and 2.2 years respectively). In miombo woodlands, fires were less frequent (median return periods of 4.5 years). Human population density had no discernible effect on the fire return intervals, but about 14% of the miombo woodlands experienced no fires over 20 years. Ongoing shifting cultivation within miombo woodlands has led to structural changes and the introduction of fire into this vegetation type where fires were rare or absent in the past. About 12% of the miombo did not burn during the period examined where people were present, whereas close to 20% of the sites remained unburnt where people were absent. This suggests that people did not change the fire return interval in any of the vegetation types studied, but that they altered the amount of the landscape that is flammable in miombo vegetation. Fires occurred between June and September, with a peak in the late dry season (August and September). Conclusions Historical research indicates that late dry-season fires are detrimental to miombo woodlands, and our analysis suggests that degradation in parts of the catchment has led to the introduction of fire to this previously fire-free and fire-sensitive vegetation type. Deforestation of miombo woodlands, and the consequent introduction of fire, is a cause for concern with respect to the ecological stability of the Okavango Delta. Managers should therefore aim to protect the remaining closed-canopy miombo stands from further clearing and to attempt to shift the timing of burns to the early dry season to reduce their intensity.Antecedentes Este trabajo presenta un análisis de los regímenes de fuegos en la pobremente estudiada cuenca del delta del Río Okavango en Bostwana. Usamos datos de MODIS para examinar la frecuencia y estacionalidad de los incendios durante 20 años (desde 2000 hasta 2020) en tres tipos vegetales dominantes (bosques de miombo, bosques abiertos de sabanas y pastizales, y arbustales bajos cerrados y abiertos), y en áreas donde había gente presente y donde ahora está ausente. Resultados La mediana del intervalo de retorno del fuego tanto para las sabanas, los pastizales y los arbustales bajos fue relativamente baja (1,9 y 2,2 años, respectivamente). En los bosques de miombo, los incendios fueron menos frecuentes (la mediana del intervalo de fuego fue de 4,5 años). La densidad de la población humana no tuvo un efecto discernible en los intervalos de retorno del fuego, aunque alrededor del 14% de los bosques de miombo no experimentaron incendios en los últimos 20 años. Las modificaciones en los cultivos dentro de los bosques de miombo llevó a cambios estructurales, y la introducción del fuego en este tipo de vegetación estuvo ausente o fue rara en el pasado. En las áreas donde la gente estuvo presente, alrededor del 12% del miombo no se quemó durante el período examinado, mientras que cerca del 20% de los sitios permanecieron sin quemarse en los lugares donde la gente estuvo ausente. Esto sugiere que la gente no cambió el intervalo de retorno del fuego en ninguno de los tipos de vegetación estudiados, en los que ellos mismos alteraron la superficie del paisaje inflamable en la vegetación del miombo. Los incendios ocurrieron entre junio y septiembre, con un pico de ocurrencia al final de la estación seca (agosto y septiembre). Conclusiones La investigación histórica indica que los incendios al final de la estación seca son detrimentales para los bosques del miombo, y nuestro análisis sugiere que la degradación en partes de esa cuenca ha llevado a la introducción del fuego en este tipo de vegetación que era previamente libre de incendios y sensible a los efectos del fuego. La deforestación de los bosques de miombo, y la consecuente introducción del fuego, es una causa de preocupación para la estabilidad ecológica del delta del Okavago. Los gestores deberían por lo tanto ayudar a proteger los remanentes de los doseles cerrados de bosques de miombo de futuros aclareos, y hacer el intento de cambiar el período de quema hacia el inicio de la estación seca para reducir su intensidad

Drivers of change and conservation needs for vertebrates in drylands: an assessment from global scale to Sahara-Sahel wetlands

Drylands range across more than half of the global terrestrial area and harbour about a quarter of continental vertebrate species, many of them endemic. However, this fauna is being increasingly threatened, in particular the one that inhabits deserts, one of the last biomes on earth. This work tracks the most relevant global change drivers acting on drylands, especially in deserts and arid regions, the conservation actions being developed, and the research needs for vertebrate conservation, following IUCN standardised classification schemes. Using the Sahara-Sahel wetlands as case study, it is provided a detailed examination of these aspects to support regional biodiversity conservation and human welfare. Deserts and arid regions are threatened by the synergistic effects of increasing development of urban areas, agriculture, energy production, mining, transportation and service corridors, resulting in pollution, invasive species, human intrusions and disturbance, biological resource overuse and in general, natural system modifications. In addition, climate change together with social underdevelopment of many desert-range countries places the mitigation of threat factors in a large and complex web of global-local societal challenges. Conservation actions targeting land/water and species protection and management, as well as education, awareness, capacity building, and legislation measures to increase livelihood development, are being developed. Additional research efforts are need to enhance biodiversity conservation planning, monitoring biodiversity and land-degradation status (based on Essential Biodiversity Variables), and quantification of socioeconomic factors associated with sustainable use of natural resources and human development. Sahara-Sahel wetlands are important life-support systems for both humans and vertebrates, the last vulnerable to listed global threats. They offer framework scenario to revert current environmental and societal challenges in deserts. Long-term conservation of desert vertebrate biodiversity requires appropriate policy instruments to promote sustainable use of natural resources. Raising environmental alertness within local communities of uniqueness of desert biodiversity is needed to promote policy change

An analysis of the recent fire regimes in the Angolan catchment of the Okavango Delta, Central Africa

CITATION: van Wilgen, B.W., de Klerk, H.M., Stellmes, M. et al., 2022. An analysis of the recent fire regimes in the Angolan catchment of the Okavango Delta, Central Africa. fire ecol 18, 13 (2022).doi.10.1186/s42408-022-00138-3The original publication is available at: https://fireecology.springeropen.com/Background: This paper presents an analysis of fire regimes in the poorly studied Angolan catchment of the Okavango Delta in Botswana. We used MODIS data to examine the frequency and seasonality of fires over 20 years (from 2000 to 2020) in three dominant vegetation types (miombo woodlands, open woodlands and grasslands, and short closed to open bushlands), and in areas where people were present, and where they were absent. Results: The median fire return intervals for both open woodlands and grasslands and short bushlands were relatively short (1.9 and 2.2 years respectively). In miombo woodlands, fires were less frequent (median return periods of 4.5 years). Human population density had no discernible effect on the fire return intervals, but about 14% of the miombo woodlands experienced no fires over 20 years. Ongoing shifting cultivation within miombo woodlands has led to structural changes and the introduction of fire into this vegetation type where fires were rare or absent in the past. About 12% of the miombo did not burn during the period examined where people were present, whereas close to 20% of the sites remained unburnt where people were absent. This suggests that people did not change the fire return interval in any of the vegetation types studied, but that they altered the amount of the landscape that is flammable in miombo vegetation. Fires occurred between June and September, with a peak in the late dry season (August and September). Conclusions: Historical research indicates that late dry-season fires are detrimental to miombo woodlands, and our analysis suggests that degradation in parts of the catchment has led to the introduction of fire to this previously firefree and fire-sensitive vegetation type. Deforestation of miombo woodlands, and the consequent introduction of fire, is a cause for concern with respect to the ecological stability of the Okavango Delta. Managers should therefore aim to protect the remaining closed-canopy miombo stands from further clearing and to attempt to shift the timing of burns to the early dry season to reduce their intensity.https://fireecology.springeropen.com/articles/10.1186/s42408-022-00138-3Publisher’s versio

Drivers of change and conservation needs for vertebrates in drylands : an assessment from global scale to Sahara-Sahel wetlands

Abstract: Drylands range across more than half of the global terrestrial area and harbour about a quarter of continental vertebrate species, many of them endemic. However, this fauna is being increasingly threatened, in particular the one that inhabits deserts, one of the last biomes on earth. This work tracks the most relevant global change drivers acting on drylands, especially in deserts and arid regions, the conservation actions being developed, and the research needs for vertebrate conservation, following IUCN standardised classification schemes. Using the Sahara-Sahel wetlands as case study, it is provided a detailed examination of these aspects to support regional biodiversity conservation and human welfare. Deserts and arid regions are threatened by the synergistic effects of increasing development of urban areas, agriculture, energy production, mining, transportation and service corridors, resulting in pollution, invasive species, human intrusions and disturbance, biological resource overuse and in general, natural system modifications. In addition, climate change together with social underdevelopment of many desert-range countries places the mitigation of threat factors in a large and complex web of global-local societal challenges. Conservation actions targeting land/ water and species protection and management, as well as education, awareness, capacity building, and legislation measures to increase livelihood development, are being developed. Additional research efforts are need to enhance biodiversity conservation planning, monitoring biodiversity and land-degradation status (based on Essential Biodiversity Variables), and quantification of socioeconomic factors associated with sustainable use of natural resources and human development. Sahara-Sahel wetlands are important life-support systems for both humans and vertebrates, the last vulnerable to listed global threats. They offer framework scenario to revert current environmental and societal challenges in deserts. Long-term conservation of desert vertebrate biodiversity requires appropriate policy instruments to promote sustainable use of natural resources. Raising environmental alertness within local communities of uniqueness of desert biodiversity is needed to promote policy change

CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence

Mediterranean Desertification and Land Degradation - Mapping Related Land Use Change Syndromes Based on Satellite Observations

Abstract In past decades, the European Mediterranean has undergone widespread land use transformations. These are largely driven by changes of socio-economic frameworks, 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 change processes on a global level, the syndrome concept was proposed to describe archetypical, co-evolutionary patterns of civilization-nature interactions (Schellnhuber et al. 1997), and has been specifically linked to the desertification issue by Downing and LUdeke (2002). In this study, we present an adaptation of the syndrome approach to the Iberian Peninsula. We suggest a data processing and interpretation framework to map the spatial extension of specific syndromes for areas occupied by natural and semi-natural vegetation. The mapping approach is based on the time series analysis of satellite data. We have characterized vegetation dynamics using NDVI estimates from the coarse scale, hypertemporal 1km MEDOKADS archive, which is based on calibrated NOAA-AVHRR images. Results indicate that local patches of abrupt disturbance, mainly by fire, are contrasted by a widespread increase in biomass, which is in large parts attributed to the abandonment of rural areas. Although this questions the dominance of classical desertification traits, i.e. decline after disturbance, it is concluded that the recent greening presents a new degradation phenomenon as it may negatively impact on fire regimes and the hydrological cycle. Keywords: Mediterranean desertification and land degradation, global change syndromes, remote sensing, time series analysis, NOAA-AVHRRJRC.H.7-Land management and natural hazard

Land Degradation Assessment and Monitoring of Drylands

This chapter provides an overview of important studies on remote sensing of land degradation in drylands. Section17.2 presents general considerations regarding the assessment and monitoring of land degradation including suitable indicators as well as sensor systems. The following sections give a review of the state of the art on the assessmentof land condition (Section 17.3), the monitoring of LUCCs to assess land degradation processes (Section 17.4), and the identification of human-induced drivers of land degradation using integrated concepts (Section 17.5), whereas Section17.6 describes limits and uncertainties regarding dryland observation. This chapter concludes with a summary of land degradation assessment and monitoring by remote sensing techniques (Section 17.7).JRC.H.5-Land Resources Managemen

On the derivation of a spatially distributed aerosol climatology for its incorporation in a radiometric Landsat pre-processing framework

<div><p>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 ecosystems where the rarity of dark objects decreases the applicability of common image-based aerosol estimation strategies and the widespread burning prohibits the use of a fixed aerosol loading. We predicted the climatological path reflectance surface by applying a multivariate regression model to all available path reflectance retrievals on basis of the geolocation and the days of the year on which the data were acquired. The resulting predictions are able to successfully model major spatio-temporal gradients of the path reflectance distribution. The prediction error (weighted root mean squared Error at 0.483 µm) was less than 1% reflectance while the prediction itself varied by 4.6% reflectance. Thus, using the modelled climatology for atmospheric correction is favourable compared to a fixed aerosol content.</p></div

Drivers of change and conservation needs for vertebrates in drylands:an assessment from global scale to Sahara-Sahel wetlands

Abstract Drylands range across more than half of the global terrestrial area and harbour about a quarter of continental vertebrate species, many of them endemic. However, this fauna is being increasingly threatened, in particular the one that inhabits deserts, one of the last biomes on earth. This work tracks the most relevant global change drivers acting on drylands, especially in deserts and arid regions, the conservation actions being developed, and the research needs for vertebrate conservation, following IUCN standardised classification schemes. Using the Sahara-Sahel wetlands as case study, it is provided a detailed examination of these aspects to support regional biodiversity conservation and human welfare. Deserts and arid regions are threatened by the synergistic effects of increasing development of urban areas, agriculture, energy production, mining, transportation and service corridors, resulting in pollution, invasive species, human intrusions and disturbance, biological resource overuse and in general, natural system modifications. In addition, climate change together with social underdevelopment of many desert-range countries places the mitigation of threat factors in a large and complex web of global-local societal challenges. Conservation actions targeting land/water and species protection and management, as well as education, awareness, capacity building, and legislation measures to increase livelihood development, are being developed. Additional research efforts are need to enhance biodiversity conservation planning, monitoring biodiversity and land-degradation status (based on Essential Biodiversity Variables), and quantification of socioeconomic factors associated with sustainable use of natural resources and human development. Sahara-Sahel wetlands are important life-support systems for both humans and vertebrates, the last vulnerable to listed global threats. They offer framework scenario to revert current environmental and societal challenges in deserts. Long-term conservation of desert vertebrate biodiversity requires appropriate policy instruments to promote sustainable use of natural resources. Raising environmental alertness within local communities of uniqueness of desert biodiversity is needed to promote policy change