Conclusions of the international workshop on
Biomass burning and its inter-relationships with the climate system
Wengen, Switzerland, September 28 – October 2, 1998-12-22

An international workshop with the title: “Biomass burning and its inter-relationships with the climate system” was held in Wengen, Switzerland, from 28 September to 2 October 1998. The workshop was attended by some 50 scientists from 12 countries. It was co-sponsored by the University of Fribourg, ENAMORS (the European Network for the development of Advanced Models to interpret Optical Remote Sensing data), the Swiss National Science Foundation and the Swiss Federal Institute for Forest, Snow and Landscape Research.

A wealth of new material was presented on the inter-relationships between climate and biomass burning. Forest fires were the subject of particular attention as a result of their world-wide prominence during the past 12 months. The period 1997-98 was characterised by a strong El Niño event, resulting in much drier conditions than normal in areas such as Indonesia and Brazil. This, in turn, resulted in many of the small-scale fires lit to clear land for agricultural activities getting out of control and spreading to primary forest areas. Devastating forest fires also occurred elsewhere, and large areas of forest were burnt in 1997-98 in areas as disparate as Canada, Russia, Mexico and Greece.

While there has been enormous progress in our understanding of how biomass burning affects climate, there are still many shortcomings. Even with the available technology and resources, it is still difficult to assess exactly the area of the Earth’s surface burnt in the last 12 months and how much of carbon dioxide and other radiatively-active greenhouse gases were released into the atmosphere. There is little doubt in the scientific community that satellite-based remote sensing systems provides the key to the global monitoring of biomass burning.  A significant amount of research has been directed towards developing new algorithms for fire detection and monitoring, which in turn, has improved estimates of the global extent of biomass burning considerably. It is expected that these capabilities will continue to improve as new satellite systems are deployed over the next several years, especially new geostationary meteorological satellites and polar-orbiting platforms such as EOS-AM (NASA), ENVISAT (ESA) and ADEOS-II (NASDA).

Scientific highlights of the meeting

New information and progress:

The 1997-98 Indonesian fires released much more carbon into the atmosphere than the oil-well fires in Kuwait following the Gulf War. The role of biomass burning as a source of precursors for photo-oxidant formation is now recognized. It is particularly important in the Tropics, and ozone derived from precursors emitted during burning has been shown to reach peak hourly concentrations of 120-150 ppb in west Africa. The significance of these phytotoxic concentrations for tropical forests requires investigation.

The detection of active fires on the basis of their thermal emissions is relatively well understood and mastered, even though the monitoring of these events with current space technologies faces definite difficulties: the polar-orbiting platforms which provide the highest and most appropriate spatial resolutions are often not observing the areas most likely to burn at the right time.  On the other hand, geostationary satellites capable of monitoring the Earth typically every half an hour do so at much lower spatial resolution and can only spot the largest fire events.  Significant progress has recently been achieved in the monitoring of active fires from space, and products are being made available operationally on the Internet by various agencies and institutions.

The assessment of the extent of burned areas, however, remains the most elusive challenge, inter alia because (1) only a fraction of the above-ground vegetation burns in uncontrolled fires, (2) the spectral response of partially burned areas is not well known, and (3) the vegetation tends to regrow quickly, at least in some ecosystems such as grasslands.  The next generation of advanced space sensors will help in this endeavour, provided substantial research and development efforts are also undertaken to define, test, and implement high performance algorithms to better extract the desired information from the measured signals.

These emerging capabilities will offer new opportunities to develop, improve and implement real-time or near-real-time applications such as fire early warning systems, and support to fire damage control activities.  The Centre de Suivi Ecologique in Dakar, Senegal has already experimented such a prototype system and is capable of warning local forest managers of the presence of fires in their areas of responsibility. Similar systems elsewhere reveal the value of the approach.

The estimation of the amount and type of smoke and particulate emissions resulting from fire activities, and the impact of these emissions on the regional climate, environment and health of the populations downwind from the burning regions will constitute the next challenge.  Addressing these issues will require interdisciplinary models capable of integrating data streams from a multiplicity of sources, at various scales and resolutions."

Future occurrence of fires
Some model predictions suggest that the frequency and intensity of fires may increase as a consequence of climate change in some areas in the future, particularly in the boreal region. This is important as about 37% of the total terrestrial global carbon pool (plant biomass and soil carbon) is contained within the boreal zone. Increases in fire frequency may be enhanced by reductions in local fire-fighting capacities (because of budget restrictions) and increased fuelwood (because of reduced prescribed burning as a result of air quality legislation). Changes in the frequency-intensity relationships of fires have considerable implications for carbon budgets, as the amount of carbon released is dependent on the nature of the fires. The changes may also bring about changes in forest species composition. Changes in the occurrence of fires in some parts of the world are believed to have already taken place as a result of climatic changes over the last 100 years.

Reliable estimates of GHG and aerosol emissions for the IPCC
Airborne measurements in smoke from biomass burning in Brazil (obtained as part of the SCAR-B Project) show that the compositions and properties of smoke particles change rapidly as smoke ages (due to condensation of gases and particle coagulation). Consequently, emission factor measurements made close to fires may not be appropriate in assessing regional and global effects of smoke on atmospheric chemical composition and the earth's radiation balance.

Although the globally-averaged direct radiative forcing due to smoke from biomass burning is probably small ( -0.3 watts per square meter (cooling)), local and regional effects can be large.

Policy implications of fire and biomass burning
Biomass burning is an important factor contributing to reduced visibility along the east coast of the USA, and has significant implications for legislation protecting visibility. Biomass burning is also likely to be important when calculating national carbon budgets. Because of increased fire activity, the strength of the North American boreal forest as a carbon sink has been reduced on the order 0.03 Gt per year over the past two decades. This has been caused by a steady increase since 1970 in the area of Canadian forests burned annually.

Several areas were identified as deserving further attention:

Mechanisms which encourage interdisciplinarity should be encouraged. This would include the organisation of further workshops along the lines of the Wengen model, with a specific goal of embracing the socio-economic research community. There is also a need to foster mechanisms for direct and regular interactions between scientists and decision makers from the local community to the government levels.

Greater exchange of scientists should occur, particularly from the countries most affected by biomass burning. This should include encouraging more scientists from less-developed countries to attend specialized workshops. There is a need to develop a harmonised terminology. This would help the exchange of information between different cultures. As in most scientific areas, capacity in developing countries should be increased, and existing mechanisms, such as the START (Global Change System for Analysis, Research and Training) programme should be strengthened.

Human resources need to keep up with remote-sensing technology. Currently, many interpretation problems are more the result of the lack of suitably qualified personnel than due to shortcomings in the available technology. Research results need to made available as quickly as possible on the Internet, and should also be made accessible to developing countries.

There is a need to link fire studies to the assessment of the sustainability of ecosystems. Fire is a highly disturbing factor for many ecosystems, with burning breaking the existing equilibrium between climate/soil conditions/land use/land cover. Examples include dry dense forests (e.g. primary dry forests on the West coast of Madagascar), seasonal semi-deciduous forests (e.g. the northern and southern edges of the Congo and Amazon Basins), coastal forests (such as mangroves), some coniferous forests (e.g. those in southern China) and others. There is therefore a real need to link the studies of fire distribution/occurrence with the sustainability of ecosystems in which fires are occurring. Within given ecosystems, burning will act as a maintenance factor; within others, it will act as a disturbing one with strong changes of the surface characteristics.

Several research priorities were also identified

1.  Priorities for better or more observations:

A new generation of Earth Observing instruments is being launched by the major national and international space agencies.  These new sensors will provide the scientific community with instruments offering much enhanced performances.  However, significant R&D support will be needed in the short term to ensure that appropriate algorithms and methods of data interpretation are designed, implemented and tested, so that much better and more reliable products and services can be delivered to the user community in a timely manner. Specifically, the spectral and directional signatures of burnt areas should be fully documented in a number of ecosystems with high priority, and made widely available to support the effective development of advanced optimized methods to analyze remote sensing data for the purpose of monitoring the extent and properties of these areas. Priorities include:

1.1 Reliable and accurate measurement of the extent of burned areas, as well as of their radiative and structural properties

1.2 Estimation of the amount and state of above-ground biomass and fuel load, but also of the quantity of peat and other underground stocks of carbon

1.3 Assessment of the burning efficiency factors and emission rates at appropriate scales and resolutions, including further emphasis on the retrieval of atmospheric chemistry data from biomass burning

1.4 Development of complete carbon accounting and its anthropogenic implications in order to quantify the terrestrial sinks?

1.5 Better quantification of several sources of greenhouse gases associated with biomass burning (e.g., agricultural residues, land-fills).

Long series of data, which are also accessible to scientists and others, are invaluable. Where such series exist, they need to be safe-guarded. In many areas, new investigations need to be started and mechanisms introduced to ensure their continuity. Such series are important as (1) they provide the effective definition of a reference condition against which any subsequent changes can be assessed, (2) they provide documentation of the natural and human-induced variability, both seasonally and from year to year, over a significant period of time, thereby providing background information on the natural or expected changes on these time scales, and (3) they answer the need for continuing monitoring during and after environmental or resource management policies have been approved and implemented, thereby enabling the evaluation of their effectiveness.

2.  Priorities for better or more accurate models:

2.1 Establishment, evaluation and operational exploitation of comprehensive dynamic models of vegetation capable of predicting the state and evolution of plant canopies, the amount of fuel, the risk of fire and the rates of gas and particulate emissions (when burning), as a function of soils and nutrients, climate, vegetation type, past fire history, etc.

3.  Priorities for validation and testing of the results:

3.1 Identification and strengthening of a global network of long-term field stations where comprehensive measurements are being made, and establishment of an agreed upon list of key variables to monitor

4.  Other critical areas of research:

4.1 Addressing scaling issues to help match local field observations with areal-averaged measurements from space, through appropriate models

4.2 Delivery of fire and biomass burning information in near-real time to the global research community, but also to managers and policy makers

4.3 Assessment of feedback of changing climate on natural forests/ecosystems/biodiversity (e.g., how would a changed climate influence the frequency / intensity / areal extent of biomass burning).

4.4 Quantification of the loss of species in sensitive ecosystem zones due to biomass burning (relevant to biodiversity) ?

4.5 Implications of biomass burning for soil quality and watersheds etc. ?

4.6 Relationships of deforestation, reforestation and afforestation activities to poverty, employment, resettlement, agriculture etc. ?

Workshop co-organisors

Prof. Martin Beniston, Department of Geography, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
Phone: +41 26 300 90 10; Fax: +41 26 300 97 46; E-Mail: Martin.Beniston@Unifr.CH

Prof. John L. Innes, Swiss Federal Institute of Forest, Snow and Landscape Research (WSL), Zuercherstrasse 111, CH-8903 Birmensdorf, Switzerland
Phone: +41 1 739 22 16; Fax: +41 1 739 22 15; E-Mail: John.Innes@wsl.CH

Prof. Michel M. Verstraete, Space Applications Institute, Joint Research Centre of the EU, I-21020 Ispra (Varese), Italy
Phone: +39 0332 78 55 07; Fax: +39 0332 78 90 73; E-Mail: michel.verstraete@jrc.it


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