Alaska Satellite Facility
Delivering Remote Sensing Data Since 1991

The Importance of Monitoring Wetlands

Among the most biologically diverse of Earth’s ecosystems, wetlands cover only ∼5% of the Earth’s ice-free land surface but exert major impacts on global biogeochemistry, hydrology, and wildlife diversity. Encompassing systems ranging from inundated forests, swamps, lakes, rivers, saltmarshes, mangroves, and poorly-drained permafrost, wetlands dominate the global methane cycle through their sensitivity to interannual and longer-term climate fluctuations and play a unique role in the transformation of biogeochemical material and as wildlife habitats for numerous species. The extent and seasonal, interannual, and decadal variation of inundated wetland area play key roles in ecosystem dynamics.

Wetlands can take the form of swamps, marshes, bogs, or fens. Despite the importance of these biomes in the global cycling of carbon and water and to current and future climate, and in part because of their complexity and inaccessibility, much about wetlands remains to be discovered including how much of the planet they occupy and details of how they affect and are affected by climate. Remote sensing gives scientists powerful tools for collecting data on wetlands distribution and dynamics. These data enable researchers to map habitat, identify vegetation types, time the rise and fall of water levels, and more. Spaceborne microwave sensing is particularly sensitive to surface water and vegetation structure, supporting monitoring of large, inaccessible areas over time regardless of atmospheric conditions or solar illumination.

NASA MEaSUREs Data Through ASF DAAC

Through the MEaSUREs (Making Earth System Data Records for Use in Research Environments) program, NASA supports development and distribution of Earth System Data Records (ESDRs), developed from remote sensing datasets and expanding understanding of the Earth system. Emphasis is placed on linking observations from multiple satellites into coherent time series datasets. MEaSUREs projects generate coherent time series datasets and facilitate the synthesis of data sets in the development of comprehensive Earth system models. MEaSUREs products are subject to rigorous standards for data quality, validation, algorithm description, documentation, and delivery.

ASF archives and distributes the ESDR datasets from the NASA Inundated Wetlands MEaSUREs  project. These inundated wetlands ESDR datasets facilitate investigations on the role of wetlands in climate, biogeochemistry, hydrology, and biodiversity.

The inundated wetlands ESDR consists of two primary components:

  1. Fine-resolution maps of wetland extent, vegetation type, and seasonal inundation dynamics, derived from Synthetic Aperture Radar (SAR) for regional and continental-scale areas covering crucial wetlands systems. These are created using data from a variety of spaceborne SARs, including the Japan Aerospace Exploration Agency’s (JAXA) Phased Array L-Band SAR (PALSAR) sensor mounted on the Advanced Land Observing Satellite (ALOS), and the associated follow-on and predecessor missions ALOS-2 PALSAR-2, and JERS-1 (the Japanese Earth Resources Satellite-1), respectively. The wetlands datasets were generated using algorithms appropriate to the nature of the wetlands systems under study, including time series and statistically-based tree classifiers.

  2. Global, coarse-resolution time series mappings of inundated area fraction at ~25 km resolution derived from multiple satellite remote sensing observations including passive and active microwave sensors and optical data sets optimized for inundation detection. The algorithm employed in the generation of this dataset employs a clustering model and a mixture model in the classification of fractional inundated areas. These datasets are provided on a bi-monthly basis for 1992-1999 and daily for 2000 onward. Annual summary products, including maximum inundated extent and annual inundation duration, are provided. A daily near real time (NRT) dataset with 2-3 day latency is also provided.

MEaSUREs at NASA DAACs

ASF focuses on synthetic aperture radar data as one of 12 theme-based NASA Earth science data centers in the nation known as Distributed Active Archive Centers (DAACs). The DAACs are major components of the Earth Observing System Data and Information System (EOSDIS), which in turn is part of NASA’s Earth Science Data Systems Program.

Links to additional MEaSUREs data at ASF and other DAACs:

This landmark, high-resolution map of Alaska wetlands, published in 2009, was created with mosaics of radar imagery. © JAXA 1993-1998.This landmark, high-resolution map of Alaska wetlands, published in 2009, was created with mosaics of radar imagery. © JAXA 1993-1998.
Get SAR Data

Get SAR Data

Select and download SAR data online using Vertex.

Use the ASF API for downloading SAR data via a command line.