Vegetation Health and Productivity Indicators for the National Climate Assessment

The sustained National Climate Assessment process is developing a system of physical, ecological, and societal indicators that communicate key aspects of the physical climate, climate impacts, vulnerabilities, and preparedness for the purpose of informing both decision makers and the public. Implementing a 14 year record of Gross and Net Primary Productivity derived from the NASA EOS MODIS satellite sensor we demonstrate how these products can serve as Ecosystem Productivity and Vegetation Health National Climate Indicators for implementation in sustained National Climate Assessments. The Net Primary Production (NPP) product combines MODIS vegetation data with daily global meteorology to calculate the annual growth of all plant material at 1 sq. km resolution. Fluctuations in NPP are used to identify regions with above or below average plant growth that may result from fluctuations in climate and can inform agricultural yield measures, carbon source/sink dynamics, and susceptibility to wildfire. The Gross Primary Productivity (GPP) product provides a high temporal resolution (8-day) metric of vegetation growth and can be used to monitor short-term vegetation response to extreme events and can also be implemented to derive vegetation phenology metrics; start, end, and length of the growing season. Implementing GPP for vegetation phenology elucidates land cover and regionally specific vegetation responses to a changing climate. For example, earlier growing season onset and longer growing season length do not necessarily coincide with increases in NPP and may instead result in large negative NPP anomalies as respiration costs escalate. High spatial resolution GPP phenology metrics can also better inform other coarse resolution metrics such as the timing of freeze-thaw transitions or growing degree day models. These Ecosystem Productivity and Vegetation Health indicators can serve as National Climate Assessment Indicators by providing regionally specific responses to a changing climate as well as complete coverage at the national scale.