(b) Tropical forest areas are ecosys- tems recognized as important pools of carbon, and in addition are important sources of NzO and possibly CH4. The result of deforestation is a large injec- tion of CO* into the atmosphere, in- creasing albedo and decreasing latent heat fluxes. NzO fluxes appear tr) be higher in grassland established after forest clearing, but it is not certain whether this high flux will be main- tained over prolonged periods. Drain- age of swamp areas in tropical forests will probably decrease CH, fluxes. Shifting cultivation is recognized as a major source of CO2 and CH.,. Reduc- tion of tropical deforestation can be achieved by providing alternatives to slash-and-burn agriculture via sustain- able management options such as agroforestry.

(c) Desertification may have a large impact on climate because bare soil surfaces are exposed during large parts of the year resulting in high albedo values, affecting the boundary layer energy fluxes and also the gener- al circulation. Afforestation and improved range management are probably the most practical ways of reversing desertification in many Mediterranean and semi-arid areas, the former at the same time supplying critical fuel wood needs.

(d) Permafrost areas are likely to release large quantities of greenhouse gases and suffer serious erosion as climate warming proceeds.

(e) Landfills will in future probably become increasingly important as urban populations in developing na- tions continue to grow. Methods of collecting gas generated in them as substitutes for fossil fuels or fuelwood deserve priority attention.

Methods

International coordination is needed to integrate flux measurements (pro- cess studies) with geographical map- ping. In this respect it is recognized that the data requirements of process studies should drive database develop ment, particularly in terms of develop- ing new data sources such as satellite sensors. Existing databases can still be used for developing a framework for

LAND USE POLICY April 1990

the ex~apolation of results of process studies from local to global scales.

A combination of measurement techniques (chamber, eddy correla- tion, gradient) is generally necessary to quantify the spatial and temporal variability of a system appropriately.

Information on the source strengths of trace gases from isotope studies has so far been underutilized, particularly as an independent constraint for glob- al tracer models.

Policies

The policy working group concen- trated on two fields: the availability of information, and sustainable land use.

Recommendations under the first heading comprised the need to pro- vide data and information - including long time series of historical data re- lated to global change studies - in a timely fashion; support national data centres that are part of established systems operated under the auspices of the ICSU, WMO, UNEP and other such agencies; and finally to take steps to keep this information available at low cost to scientists and government decision makers.

As for sustainable land use, national governments should support actions to

Conference repom

reduce slash-and-bum agriculture by improving farming practices, as well as undertaking general forest manage- ment to reduce carbon emissions and encourage the reforestation of waste- lands; they should ensure that expan- sion of agricultural and other land uses be evaluated in respect of land suita- bility; they should discourage the ex- pansion of unproductive cattle pas- tures, which is often the land use after uncontrolled forest clearing, and other unsustainable systems; they should promote gas htiesting from waste dumping landfill sites; they should pursue increases in the effectiveness of N fertilizers; and they should help develop agronomic techniques for paddy rice cultivation to reduce methane and nitrous oxide emissions without sacrificing rice yields.

A. F. Bouwman International Soil Reference

and Information Centre ~ageninge~, the ~et~dands

The conclusions and recommendations of this conference will be included, along with the conference background paper, invited papers and extended abstracts of accepted presentations, in a book to be publish~ by John Wiley & Sons, UK.

Aprh nous le deluge?

Conference on Climate and Water, convened by the World ~et~rol~i~i Organization, Helsinki, Fin/and, 1 f-75 September 1989

Humans live on land, but depend on water. Climatic changes will be felt through water-related phenomena - perhaps much more clearly than through the climatic changes them- selves.

This conference on Climate and Water brought 250 scientists from 28 countries to Helsinki. The capita1 of Finland greeted its guests with abnor- maily high temperatures - as if to increase their belief in the scenarios presented. The focus of the confer- ence was on Europe and adjacent regions. However, global change was an unavoidable perspective for many papers and discussions.

In the introductory keynote speeches, Professor Michael Budyko (USSR) and Professor Wiffrid Bach (FR Germany) presented com- plementary views on the meteorolo- gical background of climatic change. Professor Budyko based his projec- tions on past climates, particularly on the holocene optimum (5~~ years ago) and on the Pliocene (3-4 million years ago). These allowed esti- mates of a decrease in precipitation in Europe and the North American corn belt over the next decades. However, an upturn to wetter conditions would follow before 2025, including many areas that are now desert. In 2050

185

Conference report.7

agricultural productivity in Europe and North America would be con- siderably greater than it is today.

The future predicted by Professor Bach was not so optimistic. While there are many uncertainties in global circulation models (GCMs), their pro- jections of summer warming and pre- cipitation decreases could bring disas- ter to Mediterranean regions. Erosion by wind and water, loss of soil fertility, salinization, flooding, sedimentation, fire hazards, overgrazing, deforesta- tion . A complete list of possible risk factors for that region would be a long one. Additionally, the expected sea level rise will intensify marine erosion in low-lying coastal areas. Around the North Sea basin alone, this could affect 20 million people.

Professor Bach closed with a list of desirable actions, which were aimed at mitigation rather than adaptation, re- garding the latter as an unavailable option in some regions. The list in- cluded an International Convention for the Protection of the Climate, to be arranged in 1992 with the aim of agreeing an upper warming ceiling and consequent plans for reducing the ma- jor greenhouse gases.

The conference was divided into 15 sessions. One dealt with understand- ing the climate system itself, six with the effects of climate change on the hydrological cycle and eight with a wide spectrum of impacts. The follow- ing sessions were of particular interest in terms of the land use implications of climate change.

Terrestrial environment

The need to treat water and soil together was stressed by the keynote speaker on this subsession, Professor Malin Falkenmark (Sweden). Land use depends on water, both directly as in access to a water supply, and in- directly through various factors such as soil fertility. Therefore land use and water phenomena should be studied in a more integrated way in future. Pre- sent land and water policies should also be evaluated against possible fu- tures.

Would catastrophes be ‘helpful’ in changing attitudes and making com- plete policy changes possible? Profes-

186

sor Falkenmark pointed out that un- pleasant events may trigger new de- velopments, eg a restructuring of agri- culture after a number of consecutive dry years.

Another speaker in this subsession, Dr Mandych (USSR), also empha- sized the importance of the atmosphere-vegetation-soil-water system. The impending rapid climatic change would activate hydrological processes significantly faster than the natural rate of evolution of soils and vegetation cover. Erosion-induced transformation of the soil cover would be the most significant of these rapid processes.

Irrigation and drainage

In this session Professor Jaromir Nemec (WMO) discussed several methodologies for assessing the agri- cultural impacts of climatic change. Besides meeting the food needs of today’s undernourished population, world agricultural output must in- crease by 30% within the next 15 years. The measures to be taken in this difficult situation will depend on the capacity of Third World govern- ments

0 to achieve sustainable develop- ment by offsetting damage caused to the environment, and

0 to offset the impact of possible changes in climate.

The latter would not only mean im- proving food security by improving irrigation in regions increasingly sub- ject to drought. The governments con- cerned should also be able to provide sufficient drinking water and to pre- vent catastrophes that could result from increasingly frequent floods.

Flood potential

Dr Franz Nobilis (Austria) pointed out that so far relatively few studies on the impacts of climate change on flood problems have been conducted. However, there is a risk that extreme hydrological events may be more sev- erely affected than conditions as a whole. In addition to the direct influ- ence of changing patterns of precipita- tion and snowmelt, flood potential

may also be altered indirectly, eg by

changes in vegetation or soil charac- teristics.

Nobilis outlined a number of prob- lems in the assessment of flood poten- tial in the future. Improved regional scenarios should be obtained from GCMs to be used as input to improved hydrological models. Statistical tools should be developed for distinguishing and separating natural from human influences.

In addition, it was pointed out that the changing synoptic patterns of com- parable weather types in different re- gions should be studied. The financial importance of changing flood risks should also be evaluated in special cases.

Coastal zones

Considerable attention was devoted at the conference to the problems of coastal areas. The scenarios outlined by Professor Adrian Volker (the Netherlands) for the North Sea basin were as follows:

(1)

(2)

(3)

The present sea level rise of 0.2 m per century continues and forms the reference level for the other two scenarios. Superimposed on this first rise there follows after a few decades an additional rise of I m over a period of 100 years resulting from thermal expansion of the oceans. melting of glaciers and volume reductions of polar ice masses. After this period of 100 years the rise continues first at an acceler- ated rate and later more slowly. so that a sea level rise of 5 m will occur in the three centuries fol- lowing the year 2000.

Changes in the global circulation sys- tem may also increase the frequency and intensity of storm surges. Saltwa- ter intrusion into coastal groundwater aquifers may increase. Thus problems with water supply may also develop in coastal lowlands.

Professor Volker outlined three possible strategies:

(1) a planned and phased abandon- ment of the low-lying areas;

(2) a gradual adaptation as the new hydrologic conditions develop;

LAND USE POLICY April 1990

(3) the building of a new or addition-

al infrastructure for flood protec- tion and water management.

Strategy 2 can be considered the clas- sical attitude. It consists of gradually raising embankments, constructing new pumping stations, dredging new drainage canals and shifting intake points for fresh water in an upstream direction.

The implementation of strategy 3 would require a broad vision of future requirements and developments. It

consists of closing estuaries, trans- forming of embayments into freshwa- ter reservoirs and constructing an offshore vanguard dam in the North Sea. Thus a new primary line of de- fence and a new reservoir area be- tween the new dam and the existing line of defence would be created.

Esko Kuusisto National Board of Waters

and Environment Helsinki, Finland

What may and what will be grown Conference on the Greenhouse Effect and UK Agriculture, organized by the Centre for Agricultural Strategy, University of Reading, Royal Society, London, UK, 14 July 1989

A somewhat flippant but vivid picture which remains in the mind of those attending the conference must be that painted by Phillip Needham of sun- flowers on the Cairngorms. However, the aim of the conference, sponsored by the Ministry of Agriculture, Fisher- ies and Food, was a serious attempt to identify the likely effects of global warming due to the greenhouse effect on British agriculture.

In his opening address to the conference, attended by scientists

from universities and research institu- tions, farmers and representatives from conservation groups and in- terested companies. the then Minister of Agriculture, John MacGregor. said that safety margins for coastal de- fences were likely to be exceeded by three to six times in the next decade as sea levels rose, putting agricultural land, lives and properties at risk and that, although changes due to global warming would be slow, governments could not afford to sit around ‘waiting for things to happen’.

Dr John Bowman. Secretary of the National Environmental Research Council. attempted to define the na- ture and causes of the greenhouse effect from historic times and changes in greenhouse gas levels resulting from human activities. He went on to dis- cuss evidence for an enhanced green- house effect and concluded that a build-up of greenhouse gases would be

LAND USE POLICY April 1990

serious and far-reaching, ‘providing the greatest changes experienced since the last ice age’. He pointed out that while computer predictions indicate a global warming of 1.5-4.5”C with a doubling of greenhouse gas concentra- tions between the years 2030 and 2100, the effects of such warming would vary from region to region. While there is general agreement in predicting a global temperature rise, different models vary widely in predic- tions for temperature and precipita- tion.

Fertilizing effect

Following on from this, Professor Martin Parry of the Atmospheric Im- pact Research Group, University of Birmingham, in discussing the fertiliz- ing effect of CO1 said that C3 crops (wheat, barley, rice, potatoes) re- spond vigorously to CO1 enhance- ment, whereas C4 crops (maize, sor- ghum, sugarcane) do not; thus. crops in northern and central Europe stand to gain but parts of Africa may lose. On the other hand, many agricultural weeds are C3 species and would also benefit. He suggested that climatic changes could alter the geographical pattern of the world’s main food- producing regions with worldwide agricultural production costs increas- ing lO-20%. Generalizing on a poten- tial impact in the UK, he felt that the

Conference reports

implications for UK agriculture were less dramatic than for other parts of the world and offered opportunities to

the farmer.’ An increase in temperature would

extend the growing period in northern Europe where water was not limiting, but water shortage would be a prob- lem in summer. In the Mediterranean, however, growing seasons would be shorter because of warmer, drier con- ditions in spring and autumn, resulting in a shift of cropping potential within the EC from south to north. Crops currently near the northern limit of cold tolerance in the UK would be- nefit provided moisture was adequate, eg grain maize. The limit for sunflow- ers would move 500 km with a 1S”C rise, suggesting that grain maize and sunflowers could be grown in southern England in the ‘near’ future. On the other hand, yields of winter wheat varieties currently grown in south-east England would decline.

A 20% decrease in annual rainfall with the same regional and seasonal distribution as now would result in a shift westwards of the line dividing regions having more or less than 40% of farmland under cereals. Concerning upland Britain, rising temperatures would increase the upward potential limits of cultivation and, where not limited by rainfall and exposure, crop- ping potential would increase.

Following on with a discussion of the effects of water, soils, pests and diseases, Professor Parry said that in south-east England an increase in rainfall would be needed to offset increased evapotranspiration to avoid water shortages in agriculture, high costs of constructing irrigation sys- tems, reduced runoff in dry areas and resulting reductions in dilution of waste (particularly pesticide residues), and increased leaching and risks of flooding and erosion. Drought- tolerant weeds would increase in range, and warmer winters would in- crease overwintering of pests.

Turning to possible responses in agriculture, Professor Parry said that changes in temperature and rainfall could be accommodated by adjusting the timing of farming operations and there could be a shift from spring to winter cereals, to crop varieties with a

187