In February 1992 the author of this report evaluated the overall wildland fire situation in Viet Nam. He was accompanied by Dr.Ba Cuong Nguyen from the Centre des Faibles Radioactivités (Gif-sur-Yvette, France). The investigations were considered as a preparatory activity of the proposed international research campaign SEAFIRE (South East Asia FIRe Experiment), which will be operational in the mid 1990’s (for further organizational remarks: see “News from Fire Research”). The planned research campaign will focus on the emissions and atmospheric impacts of wildland fires and other plant biomass burning.
Viet Nam covers a total land area of ca. 33 million ha, of which ca. 9.3 million ha are classified as forested lands (8.6 million ha natural forests, ca. 700,000 ha forest plantations).
The main burning foci and fire problem areas were defined as follows: (1) regularly occurring fires in seasonally flammable deciduous forests, (2) wildfires in pine forest ecosystems, (3) wildfires in other natural and degraded vegetation, (4) the shifting agriculture and deforestation complex, and (5) use of fire in intensively treated agricultural lands. The peak of burning activities in Viet Nam is during the mid to late dry season (January to April).
1. Regularly occurring fires in the deciduous and semi-deciduous forests
Due to seasonal climate large tracts of Viet Nam’s forests are characterized by deciduous or semi-deciduous tree species. Both, the regular dry seasons and the seasonal availability of the shed leaves make these forests very fire prone. In many of the deciduous dipterocarp forests wildfires occur almost annually, e.g. in the Central Plateau areas near the border to Kampuchea. The dominating dipterocarps, e.g. Dipterocarpus intricatus, resprout after fires. Like in the neighbouring countries, e.g. in Kampuchea, Lao, Thailand, Myanmar, and India, the seasonal forests (or “monsoon” forests) are quite adapted to the regular occurrence of fire. Fire exclusion would lead to a progressive development toward less fire-adapted broadleaved forests.
2. Wildfires in the pine forest lands
Indigenous pine forests are occurring in submontane and montane elevations throughout Viet Nam. The main species involved are Pinus merkusii and Pinus massoniana (in the lower elevations up to ca. 1000 m a.s.l) and Pinus kesiya (above 600 m a.s.l.). These forests are occurring on an area of ca. 135,000 ha and are highly endangered by overcutting due to including illegal logging, expanding shifting agriculture, grazing practices, and increasing demands for fuelwood and charcoal production. All these activities are closely linked with the use of fire and the threat of escaping wildfires.
One of the areas with the highest wildfire risk in the Da Lat area (Lam Dong Province, northeast of Ho Chi Minh City). This mountain region is mainly populated by the Kinh, but also frequently visited by tourists from throughout the country because of the cool mountain climate and the beauty of the landscape. Both the local inhabitants and the tourists bring an increasing fire pressure to the ca. 42,000 ha of protected pine forest land. The FAO-supported project “Forest Fire and Insect Pest Management” (VIE/86/028) recently compiled the fire statistics of the period 1977-1989 (Tab.1).
Many of the pine forests are considered as fire climax communities, meaning that at certain stages of forest development (e.g. mature, open stands) the trees are not severely affected by the frequent surface fires. The understory of pine regeneration as well as the hardwoods (dipterocarps) are killed by these fires, thus resulting in an overall loss of young age classes and species diversity. Too frequent burning in general has led to severe erosion and surface runoff. This problem has been observed throughout the pine belt of the mountain zone.
Tab.1.Fire statistics of a 42,000 ha pine forest district in Da Lat area, Lam Dong Province, Viet Nam (1977-1989)
3. Wildfires in other natural and degraded vegetation
Much of the lowlands and the high plateau of Viet Nam formerly covered by seasonal or evergreen broadleaved forests is now degraded toward a shrub-tree-grass savanna. This vegetation is utilized extensively. Wildfires are occurring on a frequent base. The fires are not set for specific purposes. They are occurring largely as a result of carelessness or intentional setting without any land-treatment purpose.
The amount of former dipterocarp forest lands now degraded to a fire-climax savanna is not known exactly. It must be assumed, however, that several hundred thousands of hectares are to be classified in that category.
Other vegetation types frequently affected by fire are found in the Mekong Delta region. The economically very valuable Melaleuca leucadendron forests, which cover ca. 34,000 ha (of which 19,400 ha in Minh Hai Province), are very fire prone. Many of the wildfires are caused by honey collectors, other fires are intentionally set in order to get permission for salvage logging. During the extended pan-Pacific drought of 1982 wildfires affected more than 20,000 ha of Melaleuca forests in the Southwest of the country.
Other fire-prone vegetation types are the result of the second Indochina war. During the war approximately 12% of South Viet Nam’s forest cover was sprayed and damaged by herbicides, other forest areas were damaged by explosives, mechanical land clearing and burning operations. Formerly closed evergreen inland forests degraded to grasslands dominated by extremely flammable grasses, e.g. Imperata cylindrica and the exotic invader Pennisetum polystachyon. Fires are occurring almost annually and prevent the rehabilitation of these war-damaged forests.
4. Fire in shifting agriculture and deforestation
Fire is a traditional land clearing tool in shifting agriculture and permanent deforestation. At present the forest conversion rate is estimated to be ca. 15,000 ha per year (e.g., in 1982 the maximum forest conversion activities were 70,000 ha).
Fig.1. Forest fire prevention poster developed for publiceducation in Viet Nam (will be added later)
5. Other agricultural burnings: rice straw fires
More than 5.5 million ha of rice fields are regularly treated by fire (rice straw burning). Most of the rice straw is burned by smoldering fires. Preliminary analyses of the smoke show high concentrations of carbonyl sulfide emitted by the smoldering rice straw fires. Smoke and “smog” created by these emissions significantly affect local and regional air quality.
The general conditions of fire occurrence and fire impacts in Viet Nam is quite similar to the neighbouring countries in continental and insular Southeast Asia. It is hoped that international cooperation in fire research and assistance in fire management will enable the country to cope with the manifold fire problems in rural Viet Nam.