Perspective: Improving the accuracy of plant phenology observations and land-cover and land-use detection by optical satellite remote-sensing in the Asian tropics

Abstract

Recent advances in satellite-borne optical sensors led to important developments in the monitoring of tropical ecosystems in Asia, which have been strongly affected by recent anthropogenic activities and climate change. Based on our feasibility analyses conducted in Indonesia in Sumatra and Sarawak, Malaysia in Borneo, we discuss the current situation, problems, recent improvements, and future tasks regarding plant phenology observations and land-cover and land-use detection. We found that the Multispectral Instrument (MSI) on board the Sentinel-2A/2B satellites with a 10-m spatial resolution and 5-day observational intervals could be used to monitor phenology among tree species. For the Advanced Himawari Imager (AHI) on board the Himawari-8 geostationary satellite with a 1,000-m spatial resolution and 10-min observational intervals, we found that the time-series in vegetation indices without gaps due to cloud contamination may be used to accurately detect the timing and patterns of phenology among tree species, although the spatial resolution of the sensor requires further improvement. We also found and validated that text and pictures with geolocation information published on the Internet, and historical field notes could be used for ground-truthing land cover and land use in the past and present time. The future development of both high frequency (≤ 10 min) and high spatial resolution (≤ 10 m) optical sensors aboard satellites is expected to dramatically improve our understanding of ecosystems in the tropical Asia.

Perspective and review: how to develop our understanding of temporal changes in the relationship between people and the landscape under societal and climate change in Northeast Asia?

“…In this perspective and review paper, text mining means both the visual inspection of historical documents and data, as well as computer analyses. For example, in Japan, we can access digitized historical documents and converted PDF files of old books, old diaries, field notes, and statistics on the Web sites of museums, universities, research institutes, and the National Diet Library (e.g., Japan Search: https://jpsearch.go.jp/; Digital collection of the National Diet Library: https://dl.ndl.go.jp/en/; video and sound materials at the National Ethnology Museum: https://htq.minpaku.ac.jp/menu/ database_eng.html; the record of field work conducted in Africa, Middle East, Asia, and Oceania during the 1960s and 2010s by a team from Kyoto University in Japan: https://fieldnote.archiving.jp/, Yamada, 2015;Shin et al, 2023a). In previous studies, the paleoclimate before the advent of historical metrological observations was estimated by text mining of records related to flowering phenology of cherry (Aono and Kazui, 2008;Aono, 2015;Shin et al, 2022c), and herbaceous peony and rabbit-ear iris (Aono and Nishitani, 2022), harvest (Garnier et al, 2011;Kiss et al, 2011;Možný et al, 2012), weather, and disasters (Zaiki and Mikami, 2013;Zaiki et al, 2014;Hirano et al, 2018;Chen et al, 2020;Burgdorf et al, 2023).…”

“…It can detect the spatio-temporal variability of land surface changes in the landscape at a large scale (from local to regional) on a scale of seasons to decades. Recent technological developments have dramatically increased the spatial resolution and temporal frequency of satellite observations (Moon et al, 2021;Wu et al, 2021;Shin et al, 2023a;2023b;Wang et al, 2023). When a disaster occurs, detailed data on damage caused by landslides, floods, and tsunamis can be obtained with optical sensors and synthetic aperture radar (SAR) onboard satellites (Rao and Lin, 2011;Huyck et al, 2014;Boschetti et al, 2015;Miura and Nagai, 2020;.…”

Annually Spatial Pattern Dynamics of Forest Types under a Rapid Expansion of Impervious Surfaces: A Case Study of Hangzhou City

“…The traditional field-observed regional mapping of urban forest types is precise but costly. Satellite remote sensing techniques, such as optical sensors of Moderate Resolution Imaging Spectroradiometer (MODIS), Landsat series, and Sentinel-2, provide spatially explicit forest observations in a comparable and repeatable manner [10,11]. On account of the comparatively finer spatial resolution with a long-time sequence, the Landsat series has become a popular data source for characterizing forest dynamics [12][13][14].…”