Imaging spectroscopy investigations in wet carbon ecosystems: A review of the literature from 1995 to 2022 and future directions

Earth is experiencing unprecedented climate change driven by anthropogenic activities. The Paris Climate Agreement is the most recent international agreement pushing nations to curtail greenhouse gas emissions and balance carbon sources and sinks. To help meet the standards set forth in the Paris Climate Agreement, countries can incorporate ecosystems known to sequester and store large amounts of carbon, referred to as natural climate solutions, into their nationally determined contributions (NDC). Freshwater, brackish, and saline aquatic and wetland ecosystems (i.e., wet carbon, WC) are known for having some of the highest rates of carbon sequestration, and have the capacity to store carbon for decades to centuries. However, integration of WC into NDC is challenging due to lack of comprehensive understanding of carbon stores and fluxes (i.e., carbon state). To study the carbon state of WC ecosystems at the level that is needed for policy, use of remote sensing platforms (e.g., UAV, airborne, and spaceborne) is necessary. Imaging spectrometers, specifically hyperspectral narrow-band imagers, have the capability to provide more accurate carbon budget assessments, and discern more environmental variables that influence carbon budgets, compared to multispectral instruments. However, due to their limited availability, compared to multispectral sensors, there is a significant shortfall in imaging spectroscopy studies of WC ecosystems. This review provides an overview of previous imaging spectroscopy-WC research, highlights current knowledge gaps, and identifies future directions for research that will allow for improved study of WC ecosystems. While the past decade has seen increases in imaging spectroscopy-WC studies, we found WC habitats are globally understudied. Furthermore, the majority of research that has been done does not directly contribute to NDC efforts; however, this majority does provide the foundational work for future NDC research to be built upon. Imaging spectroscopy is a promising tool that can further advance NDC of WC ecosystems through continued development and integration.