Global Ecosystem Dynamics Investigation Lidar
Phase: Under Study
Start Date: September 2014
Program(s):Earth System Science Pathfinder
The scientific goal of the Global Ecosystem Dynamics Investigation Lidar (GEDI) is to characterize the effects of changing climate and land use on ecosystem structure and dynamics to enable radically improved quantification and understanding of the Earth's carbon cycle and biodiversity. Focused on tropical and temperate forests from its vantage point on the International Space Station (ISS), GEDI uses lidar to provide the first global, high-resolution observations of forest vertical structure. GEDI addresses three, core science questions: (Q1) What is the aboveground carbon balance of the land surface? (Q2) What role will the land surface play in mitigating atmospheric CO2 in the coming decades? (Q3) How does ecosystem structure affect habitat quality and biodiversity? Answering these questions is critical for understanding the future path of global climate change and the Earth’s biodiversity.
GEDI has four science objectives that address its core questions: (1) Quantify the distribution of above-ground carbon at fine spatial resolution; (2) Quantify changes in carbon resulting from disturbance and subsequent recovery; (3) Quantify the spatial and temporal distribution of forest structure and its relationship to habitat quality and biodiversity; (4) Quantify the sequestration potential of forests through time under changing land use and climate.
GEDI informs these science questions by making over 16 billion lidar waveform (vertical profile) observations over a nominal one year mission. The instrument uses 3 laser transmitters to produce 14 parallel tracks of 25 m footprints. From these observations a set of systematic canopy measurements is derived, the most important of which are vegetation canopy top heights and the vertical distribution of canopy leaves and branches. These measurements are then used to drive models that predict aboveground carbon at fine spatial resolution (< 500 m) (Objective 1).
GEDI's estimates of carbon are combined with the Landsat record to quantify the changes in biomass (carbon loss and carbon sequestration) that have occurred as a result of disturbance and subsequent regrowth (Objective 2).
GEDI marries ecosystem structure from lidar with ecosystem modeling to predict the sequestration potential of existing forests and to evaluate the impact of policy-driven afforestation and reforestation actions on sequestering additional carbon (objective 3).
Lastly, GEDI’s observations of ecosystem structure provide a first-ever mapping of critical habitat metrics at the fine scales required for understanding the patterns, processes, and controls on biodiversity and habitat quality (Objective 4).
Significance and Relevance to NASA Programs and Interests:
GEDI strongly supports the Science Focus Areas articulated in the Science Plan for NASA’s Science Mission Directorate, particularly for Carbon Cycle and Ecosystems. GEDI science goals respond directly to Decadal Survey observational priorities, which emphasize the need for lidar vertical structure measurements to address key challenges in carbon cycling and biodiversity. GEDI’s structure measurements also substantially enhance existing and planned NASA missions. GEDI's high biomass observations may be combined with the NASA ISRO low biomass measurements and ICESat2's boreal observations to produce global maps of biomass and provide important constraints and validation for regional scale estimates from OCO-2. GEDI further complements existing and planned pol-InSAR missions, such as DLR’s TanDEM-X, JAXA’s ALOS2 and ESA’s BIOMASS through its contribution of precisely geolocated canopy profile measurements for fusion with radar observations. Lastly, GEDI revolutionizes the previous forty years of the NASA land remote sensing archive by providing the missing vertical structure information, greatly extending land cover observations from NASA's Landsat and MODIS programs.
Principal Investigator: Ralph Dubayah (University of Maryland)
Mission Manager: Audra Bullock