Contents:

• Authors
• Abstract
• Introduction
• Science and Policy requirements
• The Approach Proposed
• The Program Strategy
• Strategic Components of the Program
• Conclusion
• References
• Table 1: Some Examples of Existing Programs and Projects
• Figure 1: Functional Linkages for a Global Land Cover Monitoring System

D.L. Skole, Basic Science and Remote Sensing Initiative, Department of Geography, Michigan State University

C. O. Justice, Global Environmental Change Program , Department of Environmental Sciences, University of Virginia

J. R.G. Townshend, Department of Geography and Institute of Advanced Computing Studies, University of Maryland

A. C. Janetos, Office of Mission to Planet Earth, National Aeronautics and Space Administration
 
 

An international system for monitoring land cover change is needed to support a range of scientific and policy objectives. Although much of the technology and methods are readily available, such a program has yet to be implemented. This paper outlines the rationale, requirements, and strategy for implementing a land cover monitoring program using satellite remote sensing, field and ground measurements, and models and assessments. The proposed program builds on existing activities throughout the world and is designed to simultaneously meet the needs of the international policy, global change research, and national resource management. Outputs from this program would provide support to the Framework Convention on Climate Change, lead to the development of consistent country-level emission inventories, and address important scientific problems in global change research such as closing the global carbon budget.

Key words: carbon cycle, emission inventories, global land cover monitoring, satellites
 
 

1.0 Introduction

Land cover change may be the most significant agent of global change: it has an important influence on hydrology, climate, and global biogeochemical cycles. In addition to its importance as an input variable to other areas of global change research, it is also an important area of study in its own right. Arguably, land cover change will have a more significant and direct influence on human habitability than climate change over the next 20 to 50 years. It is an issue with far reaching policy implications, internationally, nationally and locally. Indeed, land cover change is as inextricably linked to policy and sustainable development as it is to basic research issues.

This document provides a strategy for a global land cover change monitoring system based on remote sensing and ground based measurements. The strategy presented would link these measurements with numerical models to make quantitative assessments of the effects of land cover changes on the global environment, in particular the global carbon cycle and climate system. The strategy has a three-tier focus which fulfills the needs of: (a) the global change research community, (b) international policy initiatives such as the Framework Convention on Climate Change (FCCC) and the Intergovernmental Panel on Climate Change (IPCC), and (c) national-level resource management and mitigation efforts. 

There are three critical uncertainties in estimating the biogenic emission of greenhouse gases: 1) the rate and geographical distribution of land cover change due to deforestation and biomass burning, 2) the fate of land converted from natural land cover, and the rate of abandonment or regrowth of deforested or burned land 3) the response characteristics of carbon in vegetation and soils following disturbance. Reducing these uncertainties would increase the confidence in measurements of the human land use contribution to the global carbon cycle and its contribution to the missing carbon sink. Other efforts, however, are needed to measure and model ecosystem metabolism, particularly in undisturbed ecosystems, in order to fully close the carbon cycle and identify, locate, or explain other factors responsible for the missing sink, such as CO₂ fertilization or climatic changes.
 
 

2.0 Science and Policy Requirements

2.1 Greenhouse gas emissions and the carbon cycle. 

Human activities are largely responsible for the observed increases in atmospheric carbon dioxide. Fossil fuel burning is currently the most important source of carbon dioxide. However, biogenic sources are also important. Evidence from ice core data suggests atmospheric concentrations of CO₂ began to rise even before major inputs from fossil fuels existed. The current global net flux of carbon from land cover conversion is between 0.9 and 2.5 x 10¹⁵ g C yr^-1 (Houghton and Hackler, 1995; Houghton, 1994; Houghton et al., 1987). This represents between 18% and 49% of the release from fossil fuel combustion (Marland et al., 1994; Marland and Rotty, 1984). On a long term basis, from 1700 to 1980, the total release from the biota was approximately equal to the long term total release from fossil fuels (Houghton and Skole, 1990).

Closing the carbon budget globally or on a country basis will require improved estimates of the biotic source and sink terms. This will require annual, geographically-specific estimates of land cover change and its associated influence on carbon release and uptake using highly detailed new assessments at sub-national resolution of areas which are actively being cleared and those areas which are being released to secondary succession.

2.2 Carbon uptake in secondary growth.

Satellite data for Amazonia show extensive areas of forest regrowth and secondary growth (Alves and Skole, 1996; Steininger 1996). The impact of these large secondary growth pools on the net emissions of carbon could be significant since secondary vegetation regrowing following abandonment is a sink for carbon, but the phenomenon has yet to be quantified. Other studies of deforestation from satellite data show it is a highly dynamic process of clearing, abandonment and re-clearing, with rates related to the land use and management system that farmers employ (Skole et al., 1994; Moran et al., 1994; Walker and Homma, 1996). Understanding secondary growth as a carbon sink depends on: (1) making fine temporal resolution measurements (annually) of deforestation rates over large areas using satellite remote sensing, (2) making fine spatial and temporal scale analyses of the dynamics of land use and cover change in order to document if regrowth is a significant factor, and (3) developing an improved quantitative and diagnostic capability to determine the factors (i.e. the human dimensions) which control relative rates of clearing and regrowth from one year to the next.

2.3 Carbon uptake through changes in ecosystem metabolism.

Regional stratification of vegetation and land cover types is required for most emission models. A stratification provided by a land cover map at a spatial resolution of ~2 km would enable a framework for assigning variables such as biomass, combustion efficiencies and other necessary parameters. Beyond the classification or stratification of land cover, it is important to have a comprehensive assessment of vegetation and land cover as it relates to the seasonal patterns of vegetation phenology. Since all exchanges of gases between the atmosphere and the biota are required to close the carbon budget, information of this type is important for development of models of Net Primary Production (NPP) and ecosystem metabolism (Schimel et al., 1995). Development of climate-sensitive, process-based ecosystem models which treat the geographical and seasonal variation in phenology, NPP, and gas exchange can also be used in the development of climate response analyses. These analyses would support the IPCC process, as well as vulnerability assessments (e.g. IPCC WG II). Since this relates to undisturbed forests, comprehensive forest inventories world wide would be necessary.

2.4 Biomass burning. 

Biomass burning is frequently an important step in the land cover change process. Few studies have attempted to define regionally the relatively fine spatial (less than 20 km) and temporal (daily) distribution of biomass burning. There is as yet no global operational mechanism in place for monitoring fires, which requires daily observations (Justice et al., 1993). In the tropics there are two distinct types of anthropogenic biomass burning. The first occurs when natural ecosystems are initially cleared, often in forests, but also in savannas and grasslands. The second is repeated burning of existing savannas or pastures on a short rotation as a form of land management to maintain forage productivity. In temperate and boreal ecosystems, improved information on fire is required to address two issues. The first is gaining a better quantitative understanding of anthropogenic fires, or fire suppression, as a form of land cover change in undisturbed ecosystems. The second is understanding how the temporal frequency of natural fires may change over time in response to climatic change, and in turn influence the global budget calculations during the time period of observations (i.e. when atmospheric records exist).

2.5 Policy implications. 

Both global and country-level estimates of land cover change and greenhouse gases fluxes are poorly known. This presents major difficulties for developing international policies and mitigation strategies. For most developing countries the major source of greenhouse emissions is biogenic, rather than from fossil fuel combustion. A major new effort must be mounted to develop country-level estimates of land cover change in support of the IPCC and FCCC initiatives (Houghton et al., 1995). To do this at a country level uniformly worldwide, it will be necessary to develop consensus methodologies for measuring land cover change, development of assessments, and ensuring compliance.

Yet, despite this need for precise estimates of land cover change, an operational program of measurement, monitoring and mapping has yet to be developed. For example, comprehensive and systematic information on the extent of forest and forest loss is not available on a global basis. The latest IPCC report considers the rate of tropical deforestation to be one of the key unknowns (Houghton et al., 1995; Schimel et al., 1995). At a national level, numerous reports identify the need for accurate forest monitoring to support national forest management programs and biodiversity studies, particularly in developing countries where tropical hardwoods are an increasingly important source of foreign exchange. An accurate and up-to-date assessment of forest area and rates of depletion is fundamental to the development of improved national forest management strategies. Moreover, issues such as soil fertility and erosion, water yield, water pollution, and land use planning are directly linked to forest resource development and its management, which could benefit from such an assessment. 
 
 

3.0 The Approach Proposed

The proposed approach adopts two guiding principles: (a) build upon existing national and international programs and (b) enhance international cooperation. It also require increased inter-agency cooperation at the national level.

3.1 Building on existing programs and activities. 

The approach adopted builds on existing international and national programs and activities (See Table 1). Many existing projects and programs can provide a strong foundation for the proposed initiative; rather than duplicate such efforts, these existing studies should be integrated into a broader programmatic framework. Thus, we describe a strategy in which an international monitoring program could be quickly developed and integrated into the emerging international global change research agenda and programs. The international programs and their projects would be contributors to, and users of, the information provided by this program. The internationalization of a land cover program is seen as critical to the success of the initiative but it is equally important that the global acquisition and analysis be linked to national-level gathering of data, local access for field validation of results, production of emission inventories by national teams and collaborators and capacity building. 

In recent years several new initiatives have been focused on defining the scientific agenda for land cover change research (Meyer and Turner, 1994; Turner et al., 1994; Ojima et al., 1994; IGBP/IHDP, 1995) and the role for data and monitoring (Skole, 1994) under the auspices of the International Geosphere-Biosphere Program (IGBP) and the International Human Dimensions of Global Environmental Change Programme (IHDP) joint projects on Land Use and Cover Change (LUCC) (IGBP, 1993; IGBP, 1995). In the United States, Europe and around the world researchers and research program managers have been building the scientific, technical, and procedural underpinnings for a land cover change monitoring system. The World Forest Watch Conference held in Sao Jose dos Campos, Brazil (June 1992) provided a high-level international forum for the assessment of current approaches to satellite-based monitoring (Malingreau and Justice, 1992). The conference concluded that significant technical and methodological advancements have been made in recent years, and they are now sufficient for proceeding with an observation system which could satisfy both scientific and national-level forest management requirements. This meeting also served as a basis for forwarding recommendations from the technical and scientific communities to the policy makers and government leaders at the United Nations Conference on Environment and Development (UNCED).

In 1990 the U.S. National Aeronautics and Space Administration (NASA), in conjunction with the U.S. Environmental Protection Agency (EPA) and US Geologic Survey (USGS), began a pathfinder study for using large amounts of high resolution satellite imagery to map the rate of tropical deforestation, one of the most important land cover changes. This activity now supported as part of NASA's Mission to Planet Earth has acquired several thousand high resolution satellite images for Central Africa, Southeast Asia and the entire Amazon Basin (http://edcwww.cr.usgs.gov/landdaac/pathfinder/pathpage.html). The project is generating spatially explicit deforestation rates from the available satellite data from the mid 1970s, mid 1980s, and mid 1990s. The project is compiling a comprehensive inventory of deforestation and secondary growth to support global carbon cycle models. This project has resulted in a wide availability of these data (Skole and Tucker, 1995).

The TRopical Ecosystem Environment Observations by Satellites (TREES) project (1991-1998) and its related FIRE project are currently being implemented as a demonstration of the feasibility of applying space observation techniques to monitoring of land cover and biomass burning (http://www.mtv.sai.jrc.it/projects/treeswww/trees2.html). This project, being sponsored by the European Commission, utilizes global coverage with coarse resolution sensor systems such as the AVHRR with the all weather capability of high-resolution microwave data from ERS and JERS satellites (Mayaux and Lambin, 1997). A related project called the Global Rain Forest Mapping Mission is focused on the acquisition and evaluation of wall-to-wall microwave data is being undertaken by scientists from the Japanese Space Agency (NASDA) and NASA's Jet Propulsion Laboratory (JPL). The project focused initially on data acquisition and processing for the tropical belt but is now being extended to include the boreal zone. Regional projects using coarse resolution data have also been undertaken for temperate regions (Roy et al., 1997).

These projects demonstrate the feasibility of a global land cover monitoring system for the tropical forests. Coverage of tropical forests must be a paramount objective of any program focused on obtaining improved estimates of emissions of carbon dioxide since 90% of the current emissions come from tropical forest regions. 

The IGBP Data and Information System on behalf of the IGBP Core Projects has initiated a number of global projects which demonstrate the feasibility of other components of a global land cover monitoring program (http://www.cnrm.meteo.fr:8000/igbp/). The AVHRR 1km Project has generated a global 1km satellite product based on data contributions from a distributed network of international ground stations. The resulting data product was used by the USGS to produce a 1km global land cover product, IGBP-DIS provided the classification scheme and is currently coordinating the global product validation (Belward and Loveland, 1995). The same AVHRR 1km data base is being used by the ECE Joint Research Centre (JRC) to develop a global daily fire product. IGBP DIS provided the technical specification and is coordinating the evaluation of the product . 

The IGBP has also initiated a project to make high-resolution satellite data available to the global change research community through cooperation with the Committee on Earth Observation Satellites (CEOS), the international organization of space agencies responsible for developing and coordinating policies and standards for all remote sensing satellites. This pilot project has tested the CEOS data principles for the global change research community and has made available each year several hundred individual scenes from SPOT (the French multispectral, 20m resolution satellite), Landsat (the US multispectral 30m resolution satellite), ERS-1 (the European Space Agency's radar satellite), MOS-1 (the Japanese 50m multispectral satellite), JERS-OPS (the Japanese 18m multispectral satellite), and IRS (the Indian 30m multispectral satellite). This IGBP DIS project developed a centralized metadata query system with which users can mount an inquiry for data from all of the aforementioned platforms from one point. 
 
 

3.2 Enhancing international collaboration. 

There are also a number of established and nascent international programs which could be strengthened to contribute to the land cover program. The international nature of this global program necessitates collaboration between international programs and a strengthening of some existing bilateral programs. We recognize the pros and cons of working with the international agencies and the suggested approach is to focus international collaboration in areas of mutual benefit to the participating programs and the national participants in question.

Participation in international programs has been found to be a successful means for implementing international research and collaboration. Participation by scientists in the IGBP, IHDP and World Climate Research Program (WCRP) has proven to be effective in mobilizing the international research and monitoring community. The new joint core project of the IGBP and IHDP on Land Use and Land Cover Change (LUCC) (http://www.icc.es/lucc/) would be an important partner in this proposed program both as an information provider and information user. Similarly, IGBP-DIS has provided a useful mechanism for launching new international data initiatives in support of the science community. The newly developed international global observing systems (GCOS, CTOS and GOOS) are providing an important role in developing the requirements for operational monitoring in support of the global change community.

Programs of the international agencies such as the UNFAO and UNEP, with the mandate for monitoring the global environment, will certainly need to be considered. For example, the FAO Tropical Forest Resource Assessment Project provides an important interface to national forest agencies. Such projects can benefit from the data and information to be provided by the proposed program as well as help the program implementation. However in addition to the more traditional international agencies there are some emerging international initiatives which should be considered. For example IGBP/WCRP/IHDP System for Analysis, Research and Training (START), the Inter American Institute, ENRICH, the Asia Pacific Network (APN) and the Global Terrestrial Observing System are all addressing aspects of international networking and research and development with a focus on the global change research agenda. Such programs would provide a useful structure under which certain international aspects of this proposed land cover change program could be coordinated. International funding agencies may also be interested in helping developing countries to participate in a land cover monitoring program. For example the World Bank Global Environment Facility (GEF) is supporting several national environmental assessments that would benefit from improved land cover information and up-to-date satellite data.
 
 

4.0 The Program Strategy

The strategy adopted for the proposed program needs to be focused toward delivering required results in a timely fashion to the science and the policy communities, and yet be sufficiently flexible to accommodate changes in science and policy priorities. Such changes in focus are inevitable as uncertainties are reduced. For carbon monitoring the major uncertainties are currently known. In the short term the program should focus on these uncertainties until they are no longer the limiting uncertainties, at which point the focus should shift to new uncertainties. The land cover monitoring program although global in scope, should be sufficiently flexible to shift emphasis to different forms of land cover change and different regions.

The structure of the program would incorporate five components; (1) operational global satellite data acquisition of high- and low-spatial resolution data, (2) biomass data acquisition and modeling relying heavily on in-situ data; (3) a global emissions data base initiative to incorporate country studies outputs and new regional assessments; and to demonstrate improved emissions inventory methodologies through regional projects with national resolution; (4) regional assessments and impact studies, and (5) a synthesis and modeling component, including modeling the dynamics and human drivers of land cover change.

4.1 Program requirements. 

The proposed program has been developed around the following general requirements: 

• The program must incorporate both global and national level objectives and be capable of providing results at national, regional and global scales. 
• The information generated by the program must be useful for national level resource planning and management, as well as vulnerability studies and mitigation and adaptation planning.
• The program must include an operational monitoring system with the capability for permanent implementation. 
• The monitoring of global land cover should be reported on a 3-5 year basis with higher frequency monitoring of areas undergoing rapid transformation.
• The monitoring system should utilize data from a variety of sources and allow for in-country analyses where appropriate. 
• Data and information generated by the program must be made readily available in a timely and open fashion to a broad user community. A data system should be developed to serve the information management needs of the program and its data users.
• The information generated by the system should have a known and stated accuracy. Accuracy assessment must be an integral part of the program and field validation must be an essential component of the accuracy assessment.
• The monitoring system should be coupled to and support an independent vetting of the proposed methodology and the results should be subject to independent peer review. 

Figure 1 shows the desired functional linkages of the proposed program. The Global Land Cover Monitoring System would establish linkages to various organizations and communities that would be contributors to, and recipients of, data and information from the program. In addition, close linkages would be established with the user communities targeted by the program (e.g. global change research, the Framework Conventions, the Intergovernmental Panel on Climate Change, national monitoring programs) to clearly define the required products from the program and to provide support in the utilization of the project output. 

A close linkage would need to be established with those organizations responsible for coordinating satellite data acquisition. For example the Committee on Earth Observation Satellites (CEOS) is currently developing its role as a major player in the International Global Observing Systems and is reviewing a proposal from the space agencies and their affiliates, for an operational global forest monitoring pilot, the Global Observations of Forest Cover (GOFC) project (Janetos et al 1997) The endorsement and support of the space agencies to establish an operational satellite based land cover monitoring program would provide a critical component of the proposed monitoring system. At the satellite mission level, the Landsat Ground Station Operators Working Group and the AVHRR HRPT Ground Station Network are examples of the kind of organization that would need to be developed by the program to secure the necessary data coverage. Following the approach adopted by some of the existing precursor projects, it may be necessary to establish working relationships with local ground stations and data providers to secure the data coverage needed by the program.

The most costly component of the program is likely to be the collection of ground-based data and the validation of regional satellite data interpretations. These field-based activities will best be done in collaboration with national scientists and resource managers familiar with the local environment. For example the FAO Tropical Forest Assessment has successfully coordinated a network of national forest agencies to assist in the interpretation of sample satellite data and their validation. Similarly successful collaborations with national forest agencies have been developed by the NASA Landsat Pathfinder Humid Tropical Forest Project. The recent START initiatives of IGBP/WCRP/IHDP also provide a means for involving foreign scientists in regional global change projects (http://dis.start.org/). For example, START scientists are currently involved in the regional validation of the IGBP Global Land Cover Product. To fully engage the scientists and organizations from developing countries it is often necessary to build capacity at the institutional level. Clearly all the resources required for such a critical activity cannot be found within the budget of this program. A more appropriate approach would be to form partnerships and linkages to those agencies with the responsibility for national level capacity building such as the national and international development agencies and organizations. 

The logistical and data management aspects of this operational program will be challenging. The emerging national and international environmental information systems and data bases and the newly formed global change networks could be most helpful in providing a data management tools and structures or implementing some of project components associated with data and information. Potential data system partnerships are to be found in various national and international global change programs and amongst non-government organizations. Care needs to be taken however to balance the resources allocated to building the data and information partnerships with generating program output. 

The targeted users for the program output fall into three categories: policy and decision makers, resource managers, and global change scientists. As an example of the first category for the U.S., the EPA, DOE and the State Department would be national level users of the information and assessments generated by the program. At the UN level, global assessments by FAO and UNEP would be greatly enhanced by data and information delivered by the proposed program. The IPCC and FCCC are the ultimate targeted users for the regional/global assessments, through the various national and international channels. In the second category, resource managers concerned with national-level forest, range and agricultural management would also benefit from up-to-date satellite data and resulting assessments of national land cover. The proposed national-scale resolution of the output of the program is designed to augment national-level resource management. Similarly national organizations and international development agencies assisting in the development of national environmental plans would benefit from an up-to-date inventory of land cover and the rates of change. The biodiversity and conservation/monitoring community would also benefit from accurate spatially explicit data bases of land cover and areas of change. The global change research community would use the output of the program to drive various biogeochemical modeling, ecosystem and land use modeling efforts.
 
 

5.0 Strategic Components of the Program.

This section very briefly outlines the important strategic components of the program. Table 1 provides for each of the first four components, some examples of existing programs and projects in each of the component areas.

5.1 Strategic Component 1. Global Land Cover Assessment

Rationale. 

Global land cover stratification is needed for three major program users. First, land cover stratification is needed for designing the in-situ measurement and sampling strategy for carbon stocks and response from emission inventories. Second, a global land cover stratification is needed as an input to global terrestrial ecosystem models. Third, land cover is needed as an input to regional energy balance and climate models. A full rationale for a global land cover stratification is provided by Townshend (1992) .

Program elements

Focus 1: Global satellite based land cover classification (~1 km resolution) to be repeated every 5-10 years; hierarchical classification with a focus on carbon-relevant cover types; use of high temporal moderate to coarse resolution (daily) satellite data.

Focus 2: Direct satellite parameterization of land cover characteristics, e.g. vegetation structure and composition, % woody cover, biomass, NPP; regional- to global-scale products

Focus 3: Multi-resolution, multi-sensor approach to global mapping and stratification for global sampling

Three program elements are envisioned for the Global Land Cover Strategic Component. Focus 1 would be a global land cover classification at approximately 1 km resolution to be repeated every 5 -10 years using annual raw data. The classes for such a stratification would be relevant for carbon and ecosystem modeling and be developed using a hierarchical scheme allowing for more detailed classes to be provided from higher resolution data (Running et al., 1995). The classification would be generated using high temporal resolution satellite data from such existing global sensing systems as the NOAA-AVHRR and ATSR and future systems such as MODIS or Spot-Vegetation (e.g. Townshend et al., 1994; Running et al. 1994). Focus 2 would consist of direct satellite parameterization of land cover characteristics relevant to carbon studies, such as vegetation structure, % woody vegetation and biomass. This focus requires additional research and development although recent publications point to the feasibility of the methods (Defries et al., 1995). Focus 3 is the development of a multi-resolution approach to global land cover mapping. The approach would develop multi-level sampling using a combination of satellite data sets . The research and development for this focus would be to merge optical and microwave data and multi-resolution data sets (Conway et al., 1996).

5.2 Strategic Component 2 : Deforestation and Land Use Change

Rationale.

The conversion of forests contributes to the increase in atmospheric carbon dioxide. Recent scientific findings suggest that deforestation can also influence climate change by altering sensible and latent heat flux, planetary albedo, and surface roughness at the planetary boundary layer. More local effects include increases in the fraction of precipitation as surface run- off, soil erosion, and an eventual local decline in precipitation. Perhaps the greatest irreversible change associated with deforestation is the loss of biodiversity from habitat destruction and fragmentation.

It has now been realized that land cover change associated with deforestation is not a unidirectional process of forest conversion to agriculture. Large areas are abandoned to secondary growth. This is an important dynamic pattern which must be captured in analyses of the deforestation process since it determines the correct calculation of net emissions, and also as it is an important land use change phenomenon in its own right. Identifying location and timing of secondary growth will require careful analysis of the coupling between rates of deforestation and rates of secondary growth turn-over. The mere existence of a large second growth pool is not itself an indication of a large carbon sink; consideration must be given to the dynamics associated with this pool. 

Program elements 

Focus 1: Regional and national assessments through direct observations linked to empirical diagnostic models

Focus 2: Test sites for analysis of detailed analysis, deforestation dynamics, calibration, and field validation/accuracy.

The emphasis in this Strategic Component is high-resolution remote sensing of land cover change, in particular deforestation monitoring. Such a program element would support comprehensive analysis of land cover changes over very large regions, coupled to sampling strategies. This Strategic Component differs from the Strategic Component 1, which would utilize daily, global coverage at coarse (1-2 km) resolution, in its use of annual, regional coverage at high spatial resolution data (30 meters). While global land cover stratification/classification could be achieved at the 1-2 km resolution, precise measurement of changes in land cover will require much high resolution information.

Focus 1 would center on development of regional assessments with satellite remote sensing. This can be accomplished over large areas at fine spatial resolution (100m resolution or less), and thus can be used for tracking land cover conversions at a sub national level with a high degree of accuracy. Work done in the Brazilian Amazon and Southeast Asia has demonstrated the feasibility of this approach (Skole and Tucker, 1993; Skole et al., 1994; Skole et al., in press). This program element would also provide detailed information on rates of secondary growth creation, a potentially important carbon sink which we know very little about.

Focus 2 would be the development of studies in specific locations or countries. These studies would provide the basis for detailed analyses of the large-area analyses provided by the first program element. At one level, these studies provide a basis for field validation and accuracy assessments for the large area analyses. At another level they provide a basis for calibration of the coarse resolution satellite work done under Strategic Component 1 above. Such case studies sites also provide vital links to in-country collaborators, thereby strengthening capacity in the various countries by active engagement in research. These sites would also provide the basis for detailed temporal analysis of the dynamics of land cover change, and areas for interdisciplinary work analyzing and modeling the driving forces of land cover change.

5.3 Strategic Component 3: Biomass Burning

Rationale 

On a global scale biomass burning is one of the more important processes in land cover conversion. Biomass burning is one of the primary sources of carbon dioxide from deforestation in the humid tropics. In savanna systems it is also an important source of trace gases and particulates (Crutzen and Andreae, 1990). It should be noted though that the annual regrowth of savanna systems makes savanna burning less important as a source of carbon dioxide than burning of forests and woodlands as part of land cover transformation. In the boreal zone the stochasticity of fires is an important consideration. Biomass burning and their nonpoint source emissions are poorly documented at a national scale and accurate information is needed for national emission inventories and modeling of atmospheric chemistry .

Program elements

Focus 1: Monitoring and identification of fire locations and area burned from multiple sources of satellite data (e.g. GOES, NOAA-AVHRR, EOS-AM MODIS, DMSP).

Focus 2: Development of a database on emission factors and fuel loads.

Focus 3: Regional model estimates of gas and particulate emissions.

Satellite monitoring of fires provides information on the timing, location of fires and the annual area burned (Justice et al., 1996). The timing is important with respect to the state of the fuel load and meteorological conditions. A spatially explicit data base is needed on fire location and the area burned. the IGBP-DIS Global Fire Product demonstrates the feasibility of developing a global fire monitoring system. In addition to knowing where the fire occurs it is also important to know the fuel load or combustible biomass (Scholes et al., 1996). Currently this is performed by modeling but efforts are being made to augment the models with direct measurement procedures. The state of the fuel load with respect to moisture content is also important. The measurement and modeling of emission characteristics is based on sample in-situ measurements (Ward et al., 1996). The data from these different elements will need to managed in an information system which allows for easy access and tracking of the lineage of the data. The output from the data system should include products suitable for policy use as well as input to global atmospheric and climate modeling.

5.4 Strategic Component 4: Carbon Stocks and their Response to Disturbance 

Rationale

Data on above-ground and below-ground carbon stock are needed to turn land cover, land cover change, and biomass burning estimates from the aforementioned components into emission inventories. In addition, temporal response functions are also needed to predict how these parameters change as a result of disturbance, including anthropogenic reductions in carbon stocks within the forest as a result of thinning or degradation. To facilitate integration of this data with the land cover, deforestation, and land use databases, all of the ancillary data should be geographically referenced in a GIS in a spatial format that is compatible with the other datasets. Currently there are a few small, uncoordinated efforts to collect and develop a subset of the necessary ancillary data needed, but in order to effectively develop a global system, these efforts need to be coordinated, expanded and centralized to insure that all the necessary ancillary datasets are collected and in a format compatible with the land cover databases.

Program elements

Focus 1: Development of inventories of above and below ground carbon from existing soil pedon and biomass measurements from stand inventories found in published documents

Focus 2: Development of a new set of in-situ measurements of whole stand biomass from field measurements

Focus 3: Development of estimates of biomass production in savannas and biomass accumulation rates following disturbance in forest systems

The first focus is an analysis of forest inventory data and soil pedon databases needs to be completed. A recent initiative by IGBP-DIS to develop an improved Global Soil Pedon Data Base provides an important contribution to this objective. This focus would stress utilization of existing databases and development of a catalog of information from national forest maps and inventories, FAO timber volumes, census records, scientific literature, and other existing sources of data. The point samples of inventories could then be mapped across a land cover strata for example, based on high temporal frequency and low spatial resolution AVHRR data. 

The second focus should be to acquire a new set of in-situ measurements of whole system biomass and soil carbon. The sites for these new measurements should be carefully selected such that they along a chronosequence and along several climate gradients. This would entail detailed field studies to acquire in-situ carbon density data on above- and below-ground biomass, fine litter (e.g. leaves and twigs), woody debris, and soil organic matter. These data would be used to develop detailed expansion factors from forest inventory data to whole system biomass and soil carbon content. These field campaigns would also emphasize measurements to improve our understanding of the rates of net carbon accumulation or loss in the vegetation and soil over time and their associated response functions. This program of new field measurements should be developed to systematically cover all forested areas and engage national forestry agencies, FAO, NGOs, and local organizations within the various regions.

The third, and last, focus should be to develop models to quantify annual biomass production in grassland systems and interannual biomass accumulation in the recovering successional forests. This last focus is aimed at developing models derived from the intensive field campaigns. These models should include a landscape ecosystem production model to estimate annual biomass production in the grassland systems and forest succession model to estimate forest regrowth and carbon accumulation for areas that have been abandoned and are regrowing. 

5.5 Strategic Component 5: Analysis and Modeling

Rationale

This strategic component of the Global Land Cover Monitoring Program will provide a systematic means for synthesizing the data developed in the first four components. It is imperative as a last step to be able to integrate the land cover, deforestation and land use change, biomass burning, and ancillary datasets into geographically referenced results. Methods for deriving predictive information and synthesis of diagnostic information are necessary for providing the framework from within which emission assessments and strategic predictions can be made. This is an integral part of the program because it will provide the capability for evaluating a suite of policy scenarios.

Program Elements

Focus 1: Development and calculation of regional and national emission estimates and emissions models

Focus 2: Development of prognostic and diagnostic land cover change models, incorporating the human dimensions as drivers of change

Focus 3: Development of a prognostic capability for emissions estimates for linkage with policy

This would provide a systematic approach for making greenhouse gas emission estimates that can be used to build a world-wide emission inventory on a regular basis. This analysis and modeling effort will provide detailed insight into the biotic term of the global carbon budget. Increased understanding of the biotic term will constrain further the source and sink terms of the global carbon budget, thereby enhancing the possibility of balancing the global carbon budget. The predictive capability of the system will also provide quantitative analyses to evaluating possible policy scenarios influencing land management and land use practices. Clearly, information derived from these modeling exercises will be very useful for both the science and management communities.

Because contemporary land cover is changed mostly by human use (Turner et al., 1990), an understanding of the human dimensions of land-use change is essential to understanding land-cover change. For instance, strategic modeling of trends and locations of future land-cover change will require improved knowledge of land use since it is difficult to project future states of the land cover without knowledge of the factors that determine land use and drive land-use change. To understand the driving agents of land cover change in this way, it will be necessary to develop a program of study oriented around: (a) case studies which elucidate processes, (b) empirical diagnostic models of significant land cover changes over the last 20 years, and (c) integrated prognostic models which predict land cover change trajectories for the next 20 years.

6.0 Conclusion 

There is an urgent need for an operational land cover monitoring system to meet both policy and global change science needs. The national inventories and regional monitoring warranted by the IPCC and the FCCC have to be timely, reliable and consistent. This proposed program would contribute significantly to these national efforts as well as providing underpinning data for land management. To meet the challenges articulated by the international global change research agenda, the research community needs spatially explicit data bases of land cover and rates of change. These data would support the accurate modeling of biogeochemical cycles, atmospheric forcing and land use change, as well as provide input to assessments of climate impacts.

The authors believe that many existing programs provide sufficient demonstration of the feasibility of implementing a global land cover monitoring system. Existing international coordination bodies such as CEOS, IGBP-DIS, IGBP/IHDP-LUCC, GCOS, GTOS and WCRP provide important mechanisms for facilitating the development of different components of the proposed operational monitoring system. The regional networks such as IAI, ENRICH, APN and START provide an opportunity to facilitate the internationalization of the program.

A major component to this program will be to implement the necessary satellite data acquisition strategy. As described above, the existing suite of satellite systems and their associated monitoring projects, could provide the foundation for the proposed a global land cover monitoring system. In addition, the impending launch of improved systems within the year will greatly enhance access to the high resolution data needed to monitor land cover changes. An important first step in developing the operational system will be to develop a global scale pilot activity.

As a new global initiative, the program would require new funding. Given the scope of what is proposed, no single organization could fulfill all of the necessary functions. An open participatory interagency and international structure is needed for the program implementation. International, interagency coordination of existing and planned activities is crucial to the early success of the program. The data and information provided by this proposed program would be an important step towards better stewardship of the planet and its resources to support and sustain life. 
 
 

The authors wish to acknowledge Dr. R.A. Houghton and Dr. C. Elvidge for constructive and very thoughtful reviews of an earlier manuscript. We also wish to acknowledge the editors of this volume for their very useful comments and editorial assistance, and to the organizers of the conference. This work was supported through grants to the authors from the NASA Mission to Planet Earth Program, the NASA Landsat 7 Program, and the U.S. EPA Global Change Program.
 
 

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