|CERES No. 134 (FAO Ceres, 1992, 50 p.)|
By Vo Quy
Shortly after the war for the reunification of Vietnam ended in 1975, Vietnamese scientists tried to begin replanting what had once been the magnificent Ma Da Forest - 20000 hectares of which had been completely destroyed by the US military's herbicide spraying program.
Initial attempts to re-establish the indigenous trees failed, however, mainly because young saplings were reduced to ashes in constant grass fires sparked during the dry season. The defoliants used by the military had turned the primary forest into a vast field of easily flammable Pennisetum polystachyam, known now to local people as "American grass" (just as similar fields in the Philippines after the Second World War came to be called "Japanese grass").
"We never knew the name of the grass before", explains Tran Ba Dang, director of the Ma Da Forest Farm. "But wherever the Americans went and sprayed. only that grass can grow. After the war ended, we tried to replant Hopea odorata and Dipterocarpus dyer), but the saplings could not grow. The topsoil was very thin and poor, the humidity was very low, the temperature and the light were very high, and at last the seedlings burned up in grass fires. Finally, in 1981, we realized that we needed to establish a forest canopy under which the indigenous species could survive. We had to copy the conditions in which they used to grow in the forest.
"After we remove big areas of pernicious grass, we plant (fast-growing) shade trees, including Indigofera tenesmani, Acacia auriculiformes and Eucalyptus tereticornis. When these shade trees gain sufficient height, which takes about three years, we plant the native trees underneath them".
Today, more than 1 000 ha of Acacia, Indigofera and Eucalyptus trees give shelter to up to three different species of dipterocarp, including Dipterocarpus alatus, D. dyeri and Hopea odorata. Tran Ba Dang adds: "In the nursery, we have created the special conditions that young seedlings require, moisture and shade. This year we have about 100 000 seedlings. We also collect wild saplings and seeds from the untouched patches of the forest and cultivate these in the nursery. But it is not easy to collect the seeds of dipterocarps and reproduce them in this way. We expect the returning birds and other animals will also help the forest by scattering seeds".
The Ma Da Forest experiment offers great promise for Vietnam, but it also demonstrates how difficult, as well as time and labor-consuming, the process of rehabilitating tropical woodland is - and the vast scale of the work still required to heal our war-scarred country. Thousands of hectares that were once cool, moist, temperate and fertile are now characterized by compacted, leached earth and dry, blazing climate.
The period from 1945 to 1975 was one of almost continuous warfare in Vietnam, involving Japanese, French, American and Vietnamese armies. In the American phase, US forces employed deliberate destruction of the environment as a military tactic on a scale never seen before. This included:
spraying 72 million litres of herbicides (Agents Orange, White and Blue) on forests and
croplands (Operation Ranch Hand), resulting in the destruction of vegetation and the
residual contaminant poisoning of the land by dioxin (TCDD). An estimated 22 000
square kilometres of tropical forest and farmland were destroyed, mainly in the south of
clearing large tracts of forest, agricultural land and villages with giant bulldozers (Rome
plows) that removed even the topsoil (Operation Paul Bunyan);
burning flammable Melaleuca forests by napalm bombing in the Mekong Delta;
damaging land and forests via saturation bombing with more than 13 million tons of
bombs, equivalent to 450 times the energy of the Hiroshima atom bomb, or an average
of 265 kilograms per person in Indochina.
These actions resulted in the immediate loss of more than 20 million cubic metres of commercial timber, 300 million kilograms of food, 135 000 ha of rubber plantations, and the elimination of , much of the nation's wildlife | and fisheries. The long-term , effects are more serious, ' because, more than 20 years afterward, the forests have yet to recover.
Defoliation literally changed the face of large swaths of Vietnamese terrain. Some of the most biologically rich, and environmentally fragile, ecosystems in the world were devastated. Millions of hectares of mountainside were once a dense tropical hardwood jungle, where tigers, elephants and gaurs roamed in the forests and beautiful pheasants presented their bright colors and fantastic adornments on their display grounds. Herbicides subverted the environment; now the jungle is transmuted, as at Ma Da Forest, into savannah. The habitats of large mammals, forest birds, and the slower-breeding carnivorous animals and owls - which fed on rats - were destroyed. At the same time, the grasslands favor the breeding of vermin. Rat populations have exploded, and rats have destroyed crops and spread diseases to both cattle and humans. Bubonic plague, the "Black Death" of Europe's history, has spread rapidly in southern Vietnam since 1965.
The damage from 25 million bomb craters, which caused displacement of 3 000 million cubic metres of earth and topsoil, has also caused health hazards, the disruption of water flow, and an increase in erosion. Particles of shrapnel embedded in living trees render their wood less valuable.
Forest cover has declined even more rapidly since hostilities ceased, principally owing to agricultural clearing, forest fires, extraction of timber and firewood, and urban expansion. This has occurred first in the coastal and low-lying areas, and then gradually higher in the hills and mountains. The process is accelerating as a result of population growth. Since 1943, when 43 per cent of the nation's tree cover remained, forest cover has steadily declined - to 29 per cent in 1975-76 and to only 24 per cent by 1983. The consequences of this forest loss are particularly serious, because the country is mountainous. The resultant erosion, changes in water flow, floods and droughts are far more severe than in other countries. Most deforested areas have become barren. Almost 40 per cent of the country is now classified as unproductive wasteland.
A new revolution
But we are plotting a new revolution in Vietnam: to turn the country green again. Recalling a campaign - "Tree Planting Tet (New Year)" - launched by President Ho Chi Minh as long ago as 1959, our people are carrying out a great tree planting program, whose goal is to bring the extent of forest cover back to 50 per cent of the nation by the 21st century, in order to re-establish the ecological balance, preserve biological diversity and do our part in delaying global warming. This re-greening effort is the biggest challenge facing the country since its reunification in 1975.
In 1990,400 million trees are reported to have been planted. At 1 000 trees per hectare, this is equivalent to 400 000 ha. For the entire period 19611990, an area equal to 5.7 million ha is reported to have been planted. Our goal is to replant some 500 million trees each year, but even this is not enough to compensate for ongoing forest destruction. Millions and millions of hectares still await replanting - and we are forced to work on a shoestring budget.
In 1987, the Vietnamese Ministry of Forestry developed a plan to replant 1.5 million ha of barren hills and to step up the rehabilitation of degraded forests. Unfortunately, lack of funding and resources has thwarted these efforts (see "Casualties of Vietnam's Recovery", New Scientist, 14 September 1991).
The mangrove and Melaleuca forests in the Mekong Delta were perhaps more seriously damaged in the war than any other forest type. They were repeatedly sprayed with Agent Orange herbicide and proved particularly susceptible to its effects. In all, defoliants eliminated 124 000 ha of mangrove in southern Vietnam, about 50 per cent of the mangrove forest of the country. Almost all of the Rhizophora, Sonnerata, Bruguiera and Nypa formations died. As a result, the fisheries and shrimp catches also collapsed. University of Montana zoology professor Egbert W. Pfieffer visited the defoliated areas in 1969,1971 and 1973. Of his boat journey through a mangrove area, he said: "It was one of the most shocking experiences of my life. We saw virtually no green living plants anywhere. It was just a solid gray scene of death".
The Melaleuca forests on the peaty soil behind the mangroves proved flammable in the dry season and many were also destroyed by napalm burning.
These two most badly damaged forest ecosystems are in a more advanced state of recovery than the inland tropical forests. After the war, a program was launched to replant the mangrove forests on the areas destroyed by herbicides. Large areas were replanted with seedlings of Rhizophora apiculata, but few trees survived, probably because the soil was too compacted for their roots to take hold. In the early 1980s, a new program replanted the area and today 70000 of these seedlings survive. The mangroves now yield a self-sustaining and profit-making source of fuel and construction wood. The leaves of Rhizophora are an important link in the food chain of fish and shellfish. Fallen leaves, decomposing in the mud or tidal water, supply an enormous amount of nutrients and thus support a great variety of life, especially such invertebrates as snails, crabs, shrimp and molluscs. As a result, the fisheries are coming back and the shrimp catch rises each year. Wetland birds that had completely disappeared from their roosts during the war have also returned. More than seven major bird roosts are now protected, and new roosts appear each year.
Unique flooded forest
Melaleuca, a 10- to 20-metre tall tree with a straight trunk and small, tough leaves, forms a unique type of flooded forest in the Mekong Delta. It once covered an area of 250 000 ha in low-lying, seasonally-inundated areas. But now there are only about 116 000 ha left. Fig palms and myrtle also grew here, and beneath the canopy was a tangle of climbing vines. Years of wanton cutting for fuelwood and land clearing has gradually reduced the Melaleuca forests, leaving stands of fern or bushy Melaleuca mixed with Phragmites and other wild grasses.
During the Vietnam War, US troops attempted to drain the flooded plain area by digging canals and force the resistance army out of its bases in the Plain of Reeds, an X00 000 ha portion of the Mekong Delta. The drainage was partially successful, and once the soil was dried out sulphur rose to the surface, producing dilute sulphuric acid and reducing the soil pH to 3.9 or lower. Crops, especially rice, could not be grown. People were forced to leave.
The residual water in the canals was affected even more than the soil. Its pH was reduced to 2.8. Freshwater fish and floating rice, once rich and important sources of food for local people and wildlife, gradually disappeared. At places where the canals had been dug, water quickly drained out during the dry season. The upper cover of the soil deteriorated. Constant burning further turned the biological carpet into low brush. Finally, the spraying of the plain by US troops with toxic chemicals and napalm destroyed the Melaleuca forests.
When the war ended, local people made tremendous efforts to restore agriculture on the plain. To dilute the acidity of the soil, they dug more canals to bring in fresh water, but progress was too slow at most places to check the continued denuding.
In time, the people came to realize that to make the plain prosper as farmland again, the soil had to be well-watered in the dry season and covered again with Melaleuca. Since then, the local people have built dikes to keep the water in the plain from draining into the canals in the dry season. They have also planted Melaleuca on thousands of hectares of acid soil, since it is the only tree species that can thrive in such conditions.
Now that their habitat has begun to be restored, the natural plants and animals are gradually returning to the plain. Not only freshwater fish, but also turtles, snakes, and especially birds have returned in surprising numbers. They include some rare species, such as the Sarus Crane, Painted Stork and Adjutant. In early 1986, with the help of researchers at Hanoi University, the people of Tam Nong District set up a reserve for the cranes. Now covering about 5 000 ha, it may soon be expanded to about 9 000 ha. The number of returning cranes has increased each year, and now more than 1 000 birds have been counted.
There is a Vietnamese saying: "Birds only stay in good lands". Apparently, the efforts of the people of the Plain of Reeds and Tam Nong District to restore the land of the Tram Chim Reserve have begun to pay off. The crane is a symbol of happiness and longevity in Vietnam, as in China, Japan and many other Asian countries, and its stylized image can be found in almost all pagodas, temples and other Buddhist places of worship in Vietnam. Now that this bird has returned, our country may again become a beautiful land of peace.