Gabriela Schaepman-strub - Academia.edu (original) (raw)
Papers by Gabriela Schaepman-strub
![Research paper thumbnail of Erratum to “Capturing the fugitive: Applying remote sensing to terrestrial animal distribution and diversity” [Int. J. Appl. Earth Observ. Geoinform. 9 (2007) 1–20]](https://attachments.academia-assets.com/113069556/thumbnails/1.jpg)
](Itc Journal, May 1, 2007
Amongst many ongoing initiatives to preserve biodiversity, the Millennium Ecosystem Assessment ag... more Amongst many ongoing initiatives to preserve biodiversity, the Millennium Ecosystem Assessment again shows the importance to slow down the loss of biological diversity. However, there is still a gap in the overview of global patterns of species distributions. This paper reviews how remote sensing has been used to assess terrestrial faunal diversity, with emphasis on proxies and methodologies, while exploring prospective challenges for the conservation and sustainable use of biodiversity. We grouped and discussed papers dealing with the faunal taxa mammals, birds, reptiles, amphibians, and invertebrates into five classes of surrogates of animal diversity: (1) habitat suitability, (2) photosynthetic productivity, (3) multi-temporal patterns, (4) structural properties of habitat, and (5) forage quality. It is concluded that the most promising approach for the assessment, monitoring, prediction, and conservation of faunal diversity appears to be the synergy of remote sensing products and auxiliary data with ecological biodiversity models, and a subsequent validation of the results using traditional observation techniques.
Nature Communications, Jan 9, 2020
Biodiversity-ecosystem functioning (BEF) experiments have shown that local species richness promo... more Biodiversity-ecosystem functioning (BEF) experiments have shown that local species richness promotes ecosystem functioning and stability. Whether this also applies under realworld conditions is still debated. Here, we focus on larger scales of space, time and ecological organization. We develop a quasi-experimental design in which we relate land-cover type richness as measure of landscape richness to 17-year time series of satellite-sensed functioning in 4974 landscape plots 6.25 or 25 ha in size. We choose plots so that landscape richness is orthogonal to land cover-type composition and environmental conditions across climatic gradients. Landscape-scale productivity and temporal stability increase with landscape richness, irrespective of landscape plot size. Peak season near-infrared surface albedo, which is relevant for surface energy budgets, is higher in mixed than in single land-cover type landscapes. Effect sizes are as large as those reported from BEF-experiments, suggesting that landscape richness promotes landscape functioning at spatial scales relevant for management.
Science Advances, Jul 6, 2018
The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon fe... more The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon feedback of anywhere from 50 to 200 petagrams of carbon (Schuur et al., 2015) compromises accurate 21st-century global climate system projections. The 42-year record of atmospheric CO 2 measurements at Barrow, Alaska (71.29 N, 156.79 W), reveals significant trends in regional land-surface CO 2 anomalies (DCO 2), indicating long-term changes in seasonal carbon uptake and respiration. Using a carbon balance model constrained by DCO 2 , we find a 13.4% decrease in mean carbon residence time (50% confidence range = 9.2 to 17.6%) in North Slope tundra ecosystems during the past four decades, suggesting a transition toward a boreal carbon cycling regime. Temperature dependencies of respiration and carbon uptake suggest that increases in cold season Arctic labile carbon release will likely continue to exceed increases in net growing season carbon uptake under continued warming trends.
IEEE Transactions on Geoscience and Remote Sensing, May 1, 2018
Continuous, consistent, and long time-series from remote sensing are essential to monitoring chan... more Continuous, consistent, and long time-series from remote sensing are essential to monitoring changes on Earth's surface. However, analyzing such data sets is often challenging due to missing values introduced by cloud cover, missing orbits, sensor geometry artifacts, and so on. We propose a new and accurate spatio-temporal prediction method to replace missing values in remote sensing data sets. The method exploits the spatial coherence and temporal seasonal regularity that are inherent in many data sets. The key parts of the method are: 1) the adaptively chosen spatio-temporal subsets around missing values; 2) the ranking of images within the subsets based on a scoring algorithm; 3) the estimation of empirical quantiles characterizing the missing values; and 4) the prediction of missing values through quantile regression. One advantage of quantile regression is the robustness to outliers, which enables more accurate parameter retrieval in the analysis of remote sensing data sets. In addition, we provide bootstrap-based quantification of prediction uncertainties. The proposed prediction method was applied to a Normalized Difference Vegetation Index data set from the Moderate Resolution Imaging Spectroradiometer and assessed with realistic test data sets featuring between 20% and 50% missing values. Validation against established methods showed that the proposed method has a good performance in terms of the root-mean-squared prediction error and significantly outperforms its competitors. This paper is accompanied by the open-source R package gapfill, which provides a flexible, fast, and ready-to-use implementation of the method.
AGU Fall Meeting Abstracts, Dec 1, 2019
AGU Fall Meeting Abstracts, Dec 1, 2019
AGU Fall Meeting Abstracts, Dec 1, 2019
Carbon release through boreal fires could considerably accelerate Arctic warming; however, boreal... more Carbon release through boreal fires could considerably accelerate Arctic warming; however, boreal fire occurrence mechanisms and dynamics remain largely unknown. Here, we analyze fire activity and relevant large-scale atmospheric conditions over southeastern Siberia, which has the largest burned area fraction in the circumboreal and high-level carbon emissions due to high-density peatlands. It is found that the annual burned area increased when a positive Arctic Oscillation (AO) takes place in early months of the year, despite peak fire season occurring 1 to 2 months later. A local high-pressure system linked to the AO drives a high-temperature anomaly in late winter, causing premature snowmelt. This causes earlier ground surface exposure and drier ground in spring due to enhanced evaporation, promoting fire spreading. Recently, southeastern Siberia has experienced warming and snow retreat; therefore, southeastern Siberia requires appropriate fire management strategies to prevent massive carbon release and accelerated global warming.
AGU Fall Meeting Abstracts, Dec 1, 2016
AGU Fall Meeting 2019, Dec 10, 2019
Biodiversity and Conservation, Aug 13, 2019
With habitat loss and fragmentation among the greatest threats to biodiversity, a better understa... more With habitat loss and fragmentation among the greatest threats to biodiversity, a better understanding of the habitat use of keystone species is critical in any conservation management strategy. Aldabra Atoll, in the Seychelles archipelago, has the largest population worldwide of giant tortoises. This endemic species (Aldabrachelys gigantea) could be vulnerable to habitat fragmentation and loss induced by climate change related reduction in rainfall. Here, we assess habitat use and selection by A. gigantea in its natural environment on Aldabra. We quantified the habitat areas of A. gigantea based on the first high-resolution terrestrial habitat map of Aldabra, produced for this purpose using satellite imagery. The resulting map was combined with 4 years of movement data to assess A. gigantea habitat use and selection at landscape and home range scales. Grassland or 'tortoise turf' habitat was most preferred by A. gigantea on Aldabra, at the landscape scale across seasons, followed by open mixed scrub. These two habitats cover only 30 km 2 (19.2%) of the surface of the atoll (total area: 155.5 km 2). At the home range scale, there was no significant preference shown and habitat was used randomly. Our results suggest that Aldabra's grassland habitat, despite its small area, is of great importance to A. gigantea. Conservation management actions for A. gigantea on Aldabra and elsewhere should therefore focus on the protection and maintenance of this habitat.
Remote Sensing of Environment, May 1, 2017
Vegetation composition and water surface area are changing in many tundra regions due to climate ... more Vegetation composition and water surface area are changing in many tundra regions due to climate warming, which is twice as strong in the Arctic as compared to the global mean. Such land cover changes feed back to climate and permafrost thaw through altering the surface energy budget. We quantified
bioRxiv (Cold Spring Harbor Laboratory), Jul 13, 2022
Arctic vegetation changes, such as increasing shrub-cover, are expected to accelerate climate war... more Arctic vegetation changes, such as increasing shrub-cover, are expected to accelerate climate warming through increased absorption of incoming radiation and corresponding decrease in summer shortwave albedo. Here we analyze midsummer shortwave land-surface albedo and its change across the pan-Arctic region based on MODIS satellite observations over the past two decades (2000-2021). In contrast to expectations, we show that terrestrial midsummer shortwave albedo has not significantly changed in 82% of the pan-Arctic region, while 14% show an increase and 4% a decrease. The total median significant change was 0.014 cumulative over the past 22 years. By analyzing the visible and near-/shortwave-infrared range separately, we demonstrate that the slight increase arises from an albedo increase in the near-/shortwave infrared domain while being partly compensated by a decrease in visible albedo. A similar response was found across different tundra vegetation types. We argue that this increase in reflectance is typical with increasing biomass as a result of increased multiple reflection in the canopy. However, CMIP6 global climate model albedo predictions showed the opposite sign and different spatial patterns of snow-free summer albedo change compared to satellite-derived results. We suggest that a more sophisticated vegetation parametrization might reduce this discrepancy, and provide albedo estimates per vegetation type.
EGU General Assembly Conference Abstracts, Apr 1, 2015
AGUFM, Dec 1, 2018
The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon fe... more The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon feedback of anywhere from 50 to 200 petagrams of carbon (Schuur et al., 2015) compromises accurate 21st-century global climate system projections. The 42-year record of atmospheric CO 2 measurements at Barrow, Alaska (71.29 N, 156.79 W), reveals significant trends in regional land-surface CO 2 anomalies (DCO 2), indicating long-term changes in seasonal carbon uptake and respiration. Using a carbon balance model constrained by DCO 2 , we find a 13.4% decrease in mean carbon residence time (50% confidence range = 9.2 to 17.6%) in North Slope tundra ecosystems during the past four decades, suggesting a transition toward a boreal carbon cycling regime. Temperature dependencies of respiration and carbon uptake suggest that increases in cold season Arctic labile carbon release will likely continue to exceed increases in net growing season carbon uptake under continued warming trends.
Itc Journal, May 1, 2007
Amongst many ongoing initiatives to preserve biodiversity, the Millennium Ecosystem Assessment ag... more Amongst many ongoing initiatives to preserve biodiversity, the Millennium Ecosystem Assessment again shows the importance to slow down the loss of biological diversity. However, there is still a gap in the overview of global patterns of species distributions. This paper reviews how remote sensing has been used to assess terrestrial faunal diversity, with emphasis on proxies and methodologies, while exploring prospective challenges for the conservation and sustainable use of biodiversity. We grouped and discussed papers dealing with the faunal taxa mammals, birds, reptiles, amphibians, and invertebrates into five classes of surrogates of animal diversity: (1) habitat suitability, (2) photosynthetic productivity, (3) multi-temporal patterns, (4) structural properties of habitat, and (5) forage quality. It is concluded that the most promising approach for the assessment, monitoring, prediction, and conservation of faunal diversity appears to be the synergy of remote sensing products and auxiliary data with ecological biodiversity models, and a subsequent validation of the results using traditional observation techniques.
Nature Communications, Jan 9, 2020
Biodiversity-ecosystem functioning (BEF) experiments have shown that local species richness promo... more Biodiversity-ecosystem functioning (BEF) experiments have shown that local species richness promotes ecosystem functioning and stability. Whether this also applies under realworld conditions is still debated. Here, we focus on larger scales of space, time and ecological organization. We develop a quasi-experimental design in which we relate land-cover type richness as measure of landscape richness to 17-year time series of satellite-sensed functioning in 4974 landscape plots 6.25 or 25 ha in size. We choose plots so that landscape richness is orthogonal to land cover-type composition and environmental conditions across climatic gradients. Landscape-scale productivity and temporal stability increase with landscape richness, irrespective of landscape plot size. Peak season near-infrared surface albedo, which is relevant for surface energy budgets, is higher in mixed than in single land-cover type landscapes. Effect sizes are as large as those reported from BEF-experiments, suggesting that landscape richness promotes landscape functioning at spatial scales relevant for management.
Science Advances, Jul 6, 2018
The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon fe... more The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon feedback of anywhere from 50 to 200 petagrams of carbon (Schuur et al., 2015) compromises accurate 21st-century global climate system projections. The 42-year record of atmospheric CO 2 measurements at Barrow, Alaska (71.29 N, 156.79 W), reveals significant trends in regional land-surface CO 2 anomalies (DCO 2), indicating long-term changes in seasonal carbon uptake and respiration. Using a carbon balance model constrained by DCO 2 , we find a 13.4% decrease in mean carbon residence time (50% confidence range = 9.2 to 17.6%) in North Slope tundra ecosystems during the past four decades, suggesting a transition toward a boreal carbon cycling regime. Temperature dependencies of respiration and carbon uptake suggest that increases in cold season Arctic labile carbon release will likely continue to exceed increases in net growing season carbon uptake under continued warming trends.
IEEE Transactions on Geoscience and Remote Sensing, May 1, 2018
Continuous, consistent, and long time-series from remote sensing are essential to monitoring chan... more Continuous, consistent, and long time-series from remote sensing are essential to monitoring changes on Earth's surface. However, analyzing such data sets is often challenging due to missing values introduced by cloud cover, missing orbits, sensor geometry artifacts, and so on. We propose a new and accurate spatio-temporal prediction method to replace missing values in remote sensing data sets. The method exploits the spatial coherence and temporal seasonal regularity that are inherent in many data sets. The key parts of the method are: 1) the adaptively chosen spatio-temporal subsets around missing values; 2) the ranking of images within the subsets based on a scoring algorithm; 3) the estimation of empirical quantiles characterizing the missing values; and 4) the prediction of missing values through quantile regression. One advantage of quantile regression is the robustness to outliers, which enables more accurate parameter retrieval in the analysis of remote sensing data sets. In addition, we provide bootstrap-based quantification of prediction uncertainties. The proposed prediction method was applied to a Normalized Difference Vegetation Index data set from the Moderate Resolution Imaging Spectroradiometer and assessed with realistic test data sets featuring between 20% and 50% missing values. Validation against established methods showed that the proposed method has a good performance in terms of the root-mean-squared prediction error and significantly outperforms its competitors. This paper is accompanied by the open-source R package gapfill, which provides a flexible, fast, and ready-to-use implementation of the method.
AGU Fall Meeting Abstracts, Dec 1, 2019
AGU Fall Meeting Abstracts, Dec 1, 2019
AGU Fall Meeting Abstracts, Dec 1, 2019
Carbon release through boreal fires could considerably accelerate Arctic warming; however, boreal... more Carbon release through boreal fires could considerably accelerate Arctic warming; however, boreal fire occurrence mechanisms and dynamics remain largely unknown. Here, we analyze fire activity and relevant large-scale atmospheric conditions over southeastern Siberia, which has the largest burned area fraction in the circumboreal and high-level carbon emissions due to high-density peatlands. It is found that the annual burned area increased when a positive Arctic Oscillation (AO) takes place in early months of the year, despite peak fire season occurring 1 to 2 months later. A local high-pressure system linked to the AO drives a high-temperature anomaly in late winter, causing premature snowmelt. This causes earlier ground surface exposure and drier ground in spring due to enhanced evaporation, promoting fire spreading. Recently, southeastern Siberia has experienced warming and snow retreat; therefore, southeastern Siberia requires appropriate fire management strategies to prevent massive carbon release and accelerated global warming.
AGU Fall Meeting Abstracts, Dec 1, 2016
AGU Fall Meeting 2019, Dec 10, 2019
Biodiversity and Conservation, Aug 13, 2019
With habitat loss and fragmentation among the greatest threats to biodiversity, a better understa... more With habitat loss and fragmentation among the greatest threats to biodiversity, a better understanding of the habitat use of keystone species is critical in any conservation management strategy. Aldabra Atoll, in the Seychelles archipelago, has the largest population worldwide of giant tortoises. This endemic species (Aldabrachelys gigantea) could be vulnerable to habitat fragmentation and loss induced by climate change related reduction in rainfall. Here, we assess habitat use and selection by A. gigantea in its natural environment on Aldabra. We quantified the habitat areas of A. gigantea based on the first high-resolution terrestrial habitat map of Aldabra, produced for this purpose using satellite imagery. The resulting map was combined with 4 years of movement data to assess A. gigantea habitat use and selection at landscape and home range scales. Grassland or 'tortoise turf' habitat was most preferred by A. gigantea on Aldabra, at the landscape scale across seasons, followed by open mixed scrub. These two habitats cover only 30 km 2 (19.2%) of the surface of the atoll (total area: 155.5 km 2). At the home range scale, there was no significant preference shown and habitat was used randomly. Our results suggest that Aldabra's grassland habitat, despite its small area, is of great importance to A. gigantea. Conservation management actions for A. gigantea on Aldabra and elsewhere should therefore focus on the protection and maintenance of this habitat.
Remote Sensing of Environment, May 1, 2017
Vegetation composition and water surface area are changing in many tundra regions due to climate ... more Vegetation composition and water surface area are changing in many tundra regions due to climate warming, which is twice as strong in the Arctic as compared to the global mean. Such land cover changes feed back to climate and permafrost thaw through altering the surface energy budget. We quantified
bioRxiv (Cold Spring Harbor Laboratory), Jul 13, 2022
Arctic vegetation changes, such as increasing shrub-cover, are expected to accelerate climate war... more Arctic vegetation changes, such as increasing shrub-cover, are expected to accelerate climate warming through increased absorption of incoming radiation and corresponding decrease in summer shortwave albedo. Here we analyze midsummer shortwave land-surface albedo and its change across the pan-Arctic region based on MODIS satellite observations over the past two decades (2000-2021). In contrast to expectations, we show that terrestrial midsummer shortwave albedo has not significantly changed in 82% of the pan-Arctic region, while 14% show an increase and 4% a decrease. The total median significant change was 0.014 cumulative over the past 22 years. By analyzing the visible and near-/shortwave-infrared range separately, we demonstrate that the slight increase arises from an albedo increase in the near-/shortwave infrared domain while being partly compensated by a decrease in visible albedo. A similar response was found across different tundra vegetation types. We argue that this increase in reflectance is typical with increasing biomass as a result of increased multiple reflection in the canopy. However, CMIP6 global climate model albedo predictions showed the opposite sign and different spatial patterns of snow-free summer albedo change compared to satellite-derived results. We suggest that a more sophisticated vegetation parametrization might reduce this discrepancy, and provide albedo estimates per vegetation type.
EGU General Assembly Conference Abstracts, Apr 1, 2015
AGUFM, Dec 1, 2018
The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon fe... more The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon feedback of anywhere from 50 to 200 petagrams of carbon (Schuur et al., 2015) compromises accurate 21st-century global climate system projections. The 42-year record of atmospheric CO 2 measurements at Barrow, Alaska (71.29 N, 156.79 W), reveals significant trends in regional land-surface CO 2 anomalies (DCO 2), indicating long-term changes in seasonal carbon uptake and respiration. Using a carbon balance model constrained by DCO 2 , we find a 13.4% decrease in mean carbon residence time (50% confidence range = 9.2 to 17.6%) in North Slope tundra ecosystems during the past four decades, suggesting a transition toward a boreal carbon cycling regime. Temperature dependencies of respiration and carbon uptake suggest that increases in cold season Arctic labile carbon release will likely continue to exceed increases in net growing season carbon uptake under continued warming trends.