GCOS Terrestrial ECV T12
Above Ground Biomass

Biomass plays two major roles in the climate system: a) photosynthesis withdraws CO2 from the atmosphere and stores it as biomass; and b) quantity of biomass consumed by fire affects emissions of CO2 and of other trace gases and aerosols. Estimates of biomass change (due to land use and management practices or to natural processes) provide a direct measurement of carbon sequestration or loss and can help to validate carbon-cycle models. (Source: FAO/GTOS). Data sets below are referenced on page 11 of the ECV T12 Biomass - Assessment of the Status of the Development of the Standards for the Terrestial Essential Climate Variables (ECV), Version 10, May 25, 20099 (GTOS-67) document. More at ECV T12 Biomass FAO/GTOS web page.

Introduction: Vegetation above-ground biomass is a crucial ecological variable for understanding the evolution and potential future changes of the climate system. Vegetation biomass is a global store of carbon comparable in size to atmospheric carbon, while changes in the amount of vegetation biomass due to deforestation significantly affect the global atmosphere by acting as a net source of carbon. Vegetation systems have the potential either to sequester carbon in the future or to become an even larger source. Depending on the quantity of biomass, vegetation cover can have a direct influence on local, regional, and even global climate, particularly on air temperature and water vapour. Therefore, a global assessment of biomass and its dynamics is an essential input to climate change prognostic models and mitigation and adaptation strategies.
 
Biomass plays two major roles in the climate system: (a) photosynthesis withdraws CO2 from the atmosphere and stores it as biomass, some of which goes into long-term stores in the soil; (b) the quantity of biomass consumed by fire affects CO2, other trace gases, e.g., CH4, CO, and aerosol emissions. 
 
Only above-ground biomass is measurable with some accuracy at the broad scale, while below-ground biomass stores a large part of total carbon stocks and is rarely measured. Most nations have schemes to estimate woody biomass through forest inventories (little is recorded on non-forest biomass, except through agricultural yield statistics). This typically forms the basis for the annual reporting on forest resources required by the UNFCCC. Experimental airborne sensors have demonstrated technologies for estimating biomass (low-frequency radar, lidar) and are suitable for satellite implementation that could provide global above-ground biomass information at sub-kilometre resolutions. There are limitations to these technologies, of which some are known (for example, saturation of radar backscatter at higher levels of biomass) and some still the subject of research. 
 
National inventories of biomass differ greatly in definitions, standards, and quality, and the detailed information available at national level is normally unavailable internationally. Nonetheless, these form the basis of the country-by-country summary statistics, such as those published by the FAO in their Forest Resource Assessments.
 
Progress toward creating global gridded biomass datasets can be achieved by appropriately-designed satellite and aircraft missions, notably active microwave and laser systems. Space agencies should plan for such missions. 

(Source: WMO/IOC Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523)

Satellite Observations: Changes in land cover are important aspects of global environmental change, with implications for ecosystems, biogeochemical fluxes and global climate. Land cover change affects climate through a range of factors from albedo to emissions of greenhouse gases from the burning of biomass. Deforestation inter alia increases the amount of carbon dioxide (CO2) and other trace gases in the atmosphere. When a forest is cut and burned to establish cropland and pastures, the stored carbon joins with oxygen and is released into the atmosphere as CO2. The IPCC notes that about three-quarters of the anthropogenic emissions of CO2 to the atmosphere during the past 20 years were due to fossil fuel burning. The rest was predominantly due to land use change, especially deforestation. In 2005, a number of developing countries proposed to incorporate deforestation prevention into the Kyoto Protocol, in part through an emissions trading system. The initiative, known as REDD, (Reducing Emissions from Deforestation in Developing countries) would allow developing countries to sell emissions savings from forest conservation. Developed countries would buy the savings to credit against their own emissions targets. IGOS has set up an Integrated Global Carbon Observation (IGCO) Theme (report available from www.igospartners.org ) to develop a flexible, robust strategy for international global carbon observations over the next decade. A key component of IGCO is terrestrial carbon observations aimed at the determination of terrestrial carbon sources and sinks with increasing accuracy and spatial resolution. The IPCC has highlighted an improved understanding of carbon dynamics as vital in tackling one of the biggest environmental problems facing humanity. The IGCO work will be an essential input to the implementation of the United Nations Framework Convention on Climate Change (UNFCCC), particularly on the role of natural sinks in meeting targets under the UNFCCC Kyoto Protocol. Satellite observations allow scientists to map land cover and the dynamics of fire disturbance, and track two key elements of Earth’s vegetation – the ‘Leaf Area Index’ (LAI) and the ‘Fraction of absorbed Photo-synthetically Active Radiation’ (FAPAR). LAI is defined as the one-sided green leaf area per unit ground area in broadleaf canopies, or as the projected needle leaf area per ground unit in needle canopies. FAPAR is the fraction of photosynthetically active radiation absorbed by vegetation canopies. Both LAI and FAPAR are data necessary for understanding how Sunlight interacts with the Earth’s vegetated surfaces.

Multiple types of satellite observations are used in agricultural applications. Space imagery provides information which can be used to monitor quotas and to examine and assess crop characteristics and planting practice. Information on crop condition, for example, may also be used for irrigation management. In addition, data may be used to generate yield forecasts, which in turn may be used to optimise the planning of storage, transport and processing facilities. Classification and seasonal monitoring of vegetation types on a global basis allow the modelling of primary production – the growth of vegetation that is the base of the food chain – which is of great value in monitoring global food security. A number of radiometers provide measurements of vegetation cover, including the ATSR series, AVHRR/3, MODIS, MERIS, SEVIRI and Vegetation. These instruments are helping production of global maps of surface vegetation for modelling of the exchange of trace gases, water and energy between vegetation and the atmosphere. Multi-directional and polarimetric instruments (such as MISR and POLDER) will provide more insights into corrections of land surface images for atmospheric scattering and absorption, as well as Sun-sensor geometry, allowing better calculation of vegetation properties. Synthetic aperture radars (SARs) are used extensively to monitor deforestation and surface hydrological states and processes. The ability of SARs to penetrate cloud cover and dense plant canopies makes them particularly valuable in rainforest and high-latitude boreal forest studies. Instruments such as ASAR, SAR (RADARSAT), and PALSAR provide data for such applications as agriculture, forestry, land cover classification, hydrology and cartography. CEOS and GCOS have concluded that many of the Essential Climate Variables related to vegetation and supported from space will require reprocessing of the moderate resolution historical record (in particular AVHRR) to be of greater value for climate purposes, and appropriate actions have been defined, including the development of enhanced calibration and validation schemes which guarantee long-term stability and consistency over different temporal and spatial scales. Research topics like scaling, and the development of ‘community radiative transfer models’ integrated into sophisticated assimilation schemes, are of paramount importance for an integrated approach. (Satellite Missions) (Source: CEOS EO Handbook - Earth Observations Plans by Measurement)

References:

• Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) GCOS-138/GOOS-184/GTOS-76/WMO-TD/No. 1523
• The Second Report on the Adequacy of the Global Observing Systems for Climate in Support of the UNFCCC - April 2003 (GCOS-82/WMO/TD Noc 1143)
• ECV T12 Biomass - Assessment of the Status of the Development of the Standards for the Terrestial Essential Climate Variables (ECV), Version 10, 25 May 2009
• CEOS EO Handbook - Earth Observations Plans by Measurement
• CEOS EO Handbook - Measurement Categories (Updated October 2010)

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