Frank Thonfeld

Dr. Frank Thonfeld

German Aerospace Center (DLR)
orcid

Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
25 January 2022 in Remote Sensing
Verified
Journal Article
Open access
PDF file
FTFrank Thonfeld
Frank Thonfeld
UGUrsula Gessner
Ursula Gessner
SHStefanie Holzwarth
Stefanie Holzwarth
JKJennifer Kriese
Jennifer Kriese
EPEmmanuel Da Ponte
Emmanuel Da Ponte
CKClaudia Kuenzer
Claudia Kuenzer
Central Europe was hit by several unusually strong periods of drought and heat between 2018 and 2020. These droughts affected forest ecosystems. Cascading effects with bark beetle infestations in spruce stands were fatal to vast forest areas in Germany. We present the first assessment of canopy cover loss in Germany for the period of January 2018–April 2021. Our approach makes use of dense Sentinel-2 and Landsat-8 time-series data. We computed the disturbance index (DI) from the tasseled cap components brightness, greenness, and wetness. Using quantiles, we generated monthly DI composites and calculated anomalies in a reference period (2017). From the resulting map, we calculated the canopy cover loss statistics for administrative entities. Our results show a canopy cover loss of 501,000 ha for Germany, with large regional differences. The losses were largest in central Germany and reached up to two-thirds of coniferous forest loss in some districts. Our map has high spatial (10 m) and temporal (monthly) resolution and can be updated at any time.

1 August 2016 in International Journal of Applied Earth Observation and Geoinformation
Verified
Journal Article
Closed access
FTFrank Thonfeld
Frank Thonfeld
HFHannes Feilhauer
Hannes Feilhauer
MBMatthias Braun
Matthias Braun
GMGunter Menz
Gunter Menz

11 December 2019 in Sustainability
Verified
Journal Article
Open access
PDF file
KNKristian Näschen
Kristian Näschen
BDBernd Diekkrüger
Bernd Diekkrüger
MEMariele EVERS
Mariele EVERS
Britta HöllermannBritta Höllermann
Britta Höllermann
SSStefanie Steinbach
Stefanie Steinbach
FTFrank Thonfeld
Frank Thonfeld
Many parts of sub-Saharan Africa (SSA) are prone to land use and land cover change (LULCC). In many cases, natural systems are converted into agricultural land to feed the growing population. However, despite climate change being a major focus nowadays, the impacts of these conversions on water resources, which are essential for agricultural production, is still often neglected, jeopardizing the sustainability of the socio-ecological system. This study investigates historic land use/land cover (LULC) patterns as well as potential future LULCC and its effect on water quantities in a complex tropical catchment in Tanzania. It then compares the results using two climate change scenarios. The Land Change Modeler (LCM) is used to analyze and to project LULC patterns until 2030 and the Soil and Water Assessment Tool (SWAT) is utilized to simulate the water balance under various LULC conditions. Results show decreasing low flows by 6–8% for the LULC scenarios, whereas high flows increase by up to 84% for the combined LULC and climate change scenarios. The effect of climate change is stronger compared to the effect of LULCC, but also contains higher uncertainties. The effects of LULCC are more distinct, although crop specific effects show diverging effects on water balance components. This study develops a methodology for quantifying the impact of land use and climate change and therefore contributes to the sustainable management of the investigated catchment, as it shows the impact of environmental change on hydrological extremes (low flow and floods) and determines hot spots, which are critical for environmental development.

24 September 2016 in Remote Sensing
Verified
Journal Article
Open access
PDF file
JMJavier Muro
Javier Muro
MCMorton Canty
Morton Canty
KCKnut Conradsen
Knut Conradsen
CHChristian Hüttich
Christian Hüttich
ANAllan Nielsen
Allan Nielsen
GMGunter Menz
Gunter Menz
Automated monitoring systems that can capture wetlands’ high spatial and temporal variability are essential for their management. SAR-based change detection approaches offer a great opportunity to enhance our understanding of complex and dynamic ecosystems. We test a recently-developed time series change detection approach (S1-omnibus) using Sentinel-1 imagery of two wetlands with different ecological characteristics; a seasonal isolated wetland in southern Spain and a coastal wetland in the south of France. We test the S1-omnibus method against a commonly-used pairwise comparison of consecutive images to demonstrate its advantages. Additionally, we compare it with a pairwise change detection method using a subset of consecutive Landsat images for the same period of time. The results show how S1-omnibus is capable of capturing in space and time changes produced by water surface dynamics, as well as by agricultural practices, whether they are sudden changes, as well as gradual. S1-omnibus is capable of detecting a wider array of short-term changes than when using consecutive pairs of Sentinel-1 images. When compared to the Landsat-based change detection method, both show an overall good agreement, although certain landscape changes are detected only by either the Landsat-based or the S1-omnibus method. The S1-omnibus method shows a great potential for an automated monitoring of short time changes and accurate delineation of areas of high variability and of slow and gradual changes.

31 October 2020 in Remote Sensing
Verified
Journal Article
Open access
PDF file
SHStefanie Holzwarth
Stefanie Holzwarth
FTFrank Thonfeld
Frank Thonfeld
SASahra Abdullahi
Sahra Abdullahi
SASarah Asam
Sarah Asam
EPEmmanuel Da Ponte
Emmanuel Da Ponte
CKClaudia Kuenzer
Claudia Kuenzer
Forests in Germany cover around 11.4 million hectares and, thus, a share of 32% of Germany’s surface area. Therefore, forests shape the character of the country’s cultural landscape. Germany’s forests fulfil a variety of functions for nature and society, and also play an important role in the context of climate levelling. Climate change, manifested via rising temperatures and current weather extremes, has a negative impact on the health and development of forests. Within the last five years, severe storms, extreme drought, and heat waves, and the subsequent mass reproduction of bark beetles have all seriously affected Germany’s forests. Facing the current dramatic extent of forest damage and the emerging long-term consequences, the effort to preserve forests in Germany, along with their diversity and productivity, is an indispensable task for the government. Several German ministries have and plan to initiate measures supporting forest health. Quantitative data is one means for sound decision-making to ensure the monitoring of the forest and to improve the monitoring of forest damage. In addition to existing forest monitoring systems, such as the federal forest inventory, the national crown condition survey, and the national forest soil inventory, systematic surveys of forest condition and vulnerability at the national scale can be expanded with the help of a satellite-based earth observation. In this review, we analysed and categorized all research studies published in the last 20 years that focus on the remote sensing of forests in Germany. For this study, 166 citation indexed research publications have been thoroughly analysed with respect to publication frequency, location of studies undertaken, spatial and temporal scale, coverage of the studies, satellite sensors employed, thematic foci of the studies, and overall outcomes, allowing us to identify major research and geoinformation product gaps.

1 August 2018 in International Journal of Applied Earth Observation and Geoinformation
Verified
Journal Article
Closed access
JMJavier Muro
Javier Muro
ASAdrian Strauch
Adrian Strauch
SHSascha Heinemann
Sascha Heinemann
SSStefanie Steinbach
Stefanie Steinbach
FTFrank Thonfeld
Frank Thonfeld
BDBernd Diekkrüger
Bernd Diekkrüger