TABLE OF CONTENTS ROLE OF BOREAL SOIL'S METHANE CONSUMPTION READERS WRITE JAPAN-CANADA PANEL ON GLOBAL CHANGE AND THE NORTH PACIFIC NEW REPORT IDENTIFIES MAJOR WATER ISSUES FACING CANADA CANADIAN ENVIRONMENTAL ASSESSMENT AGENCY RECEIVES INTERNATIONAL AWARD CGCP NOW ACFAS SYMPOSIUM ON SUCCESS ATMOSPHERIC CHANGE IN CANADA: ASSESSING THE WHOLE AS WELL AS THE PARTS U.S. HUMAN DIMENSIONS MEETING CCP Info THE CANADIAN CLIMATE PROGRAM: ACHIEVEMENTS 1990-1994 FINAL WORKSHOP PLANNED FOR THE MACKENZIE BASIN IMPACT STUDY SECOND LOICZ OPEN SCIENCE MEETING FREE-AIR CO2 ENRICHMENT EXPERIMENT IN FOREST CANADIAN CONTRIBUTIONS TO THE INTERNATIONAL HUMAN DIMENSIONS PROGRAMME INTER-AMERICAN INSTITUTE IS UP AND RUNNING FUTURE OF LONG-TERM ECOLOGICAL DATA QUESTIONNAIRE   RECENT PUBLICATIONS POLITICAL RESPONSE TO CLIMATE CHANGE LUKEWARM EVENTS CALENDAR

READERS WRITE Thawing Permafrost I believe that Dr. McAllister [in his letter to DELTA, Vol. 5, No. 4, Winter 1994 — "Effect of Climatic Warming on Taiga?", p. 2] observed thermokarst development in a peatland: freshly flooded areas with dead, fallen trees. When permafrost develops in a peatland, the surface rises well above the water table as the frozen core expands. Trees will be able to grow on this drier surface. However, if for some reason the permafrost begins to thaw, the surface sinks to its original level, becomes flooded by the water in the peatland and the trees die. Such areas are readily recognizable, and are called "collapse scars". This process is reasonably well understood after three decades of study by a number of scientists. We know that the thawing of permafrost is usually triggered by a catastrophic event, such as fire or a change in hydrology. We noted, however, that permafrost degradation is widespread along its southern limit where the temperature of the permafrost is barely below freezing. Air photos taken at different times, tree ring studies, and peat accumulation rates show that thawing of permafrost at its southern limit became widespread after the mid-1880's and it has accelerated since the early 1900's. This corresponds reasonably well with the instrumented rise of the mean annual temperature in west-central Canada. Much of this information is available in scientific journals. S.C. Zoltai Canadian Forest Service Northern Forestry Centre, Edmonton, Alberta