Forests - a planetary treasure

Posted: 1 August 2000

Author: Norman Myers

The decline of tropical forests represents the biggest land-use change of its scale and speed in human history. It may soon by followed by a similar decline of boreal (northern) forests. Yet, says Norman Myers we have scarcely begun to ask ourselves what we are losing along the way. Here he explores the real nature of this forest treasure house and tots up some of the damaging consequences of grandscale destruction.

© WWF Michel Roggo

The value of forests lies in much more than the wood supplies they contain. Yet commercial timber and other wood products are worth well over $400 billion per year, and demand for them is expected to increase by half by 2010. Unfortunately there are signs of a timber famine ahead. Already there is a growing shortage of tropical hardwoods.

Tropical forest countries used to earn as much from timber exports as from cotton and twice as much as from rubber, but due to over-harvesting of timber these revenues are declining fast, and many major exporters have become importers.

Still more important is fuelwood for developing countries, with three billion people who depend on it for almost all their household energy. Already half of these people cannot obtain fuelwood without overcutting tree stocks, and many of them find it is as hard to heat the supper bowl as to fill it. Worse, their total is expected to rise to 2.5 billion by 2010.

Because of shortages, many rural families now spend between 1.5 and 5 hours each day collecting fuelwood. The opportunity costs of this time, which could be better spent on tilling cropfields and other productive work, is thought to be around $50 billion per year. This figure is to be compared with the cost of a comprehensive fuelwood-plantation programme, $12 billion per year - a figure often regarded as "quite impossible".

Genetic resources

Forests are the main home of Earth's species. While covering only six per cent of the planet's land surface, tropical forests contain at least 50 per cent, possibly 70 per cent and conceivably 90 per cent of all species. Half a square kilometre of Malaysia's forests can feature as many tree and shrub species as the whole of the United States and Canada, while a single bush in Peruvian Amazonia has revealed as many ant species as in the British Isles.

When we visit our neighbourhood chemist, there is one chance in four that our purchase - whether a drug, medicinal or pharmaceutical - owes its manufacture to startpoint materials from tropical-forest plants. These products include antibiotics, antivirals, analgesics, tranquillizers, diuretics and laxatives, among many other items. The contraceptive pill has been based upon forest-plant materials from Mexico and West Africa.

Commercial sales of these diverse products are worth some $40 billion a year in the developed world, while their economic value can be several times as large. The rosy periwinkle from Madagascar has supplied alkaloids that form the basis of two potent therapies against blood cancers, with economic benefits worth at least $1 billion per year.

Tropical forests are reckoned to contain another dozen plant species with capacity to generate superstar drugs against other forms of cancer, provided the plants can be identified before they lose their habitats.

We enjoy these plant contributions to our health after pharmacologists have taken a cursory look at only one plant species in ten, and an intensive look at only one plant species in a hundred. We can surely look forward to entire pharmacopoeias of new products, provided the forests and their species survive. One of the most promising responses to AIDS could stem from a plant of Queensland's forests.

Other forms of biodiversity assist our material welfare. The most numerous forest species by a long way are insects. One might suppose that if we are losing perhaps 50 insect species in tropical forests every day, it hardly matters: what have creepy-crawlies done for us? But consider the oil-palm plantations of Peninsular Malaysia.

Until 1980, pollination of the palm trees was undertaken by human hand, an inefficient and expensive process. The plantation owners asked themselves how the palm got itself pollinated in its native habitats of Cameroon's forests. It turned out the task was performed by a tiny weevil. The plantation owners brought back a stock of weevils to Malaysia for release into the plantations, where they performed admirably, with savings reckoned at $120 million in 1981. We can thank that weevil next time we use margarine and cosmetics that may well be based on palm oil.

Wild species and their genetic resources also support agriculture. Asia's rice crop was hit in the early 1970s by a "grassy stunt" virus that threatened to devastate 300,000 square kilometres of rice fields. Fortunately a single gene from a wild rice in an Indian forest offered resistance against the virus. In 1976 there emerged another virus, known as "ragged stunt" disease, and again the most potent source of resistance proved to be a wild forest rice. In India alone, the introduction of wild rice strains (plus primitive cultivars) has increased yields by $75 million a year.

Many other crops - ranging from food crops such as avocado, banana, cashew, coconut, grapefruit and lemon to beverages and spices such as cacao, cinnamon, coffee, paprika and vanilla, and to industrial crops such as oil palm and rubber - depend for part of their productivity and disease resistance, on genetic infusions from wild relatives in tropical forests. Just the exports of these crops are worth well over $20 billion a year.

Environmental services

Now consider the environmental services supplied by forests, even more bountiful and valuable than material goods. Watershed services, for instance: deforestation of upland catchments can lead to disruption of hydrological systems, causing year-round water flows in downstream areas to give way to flood-and-drought regimes.

In the Ganges Valley with its 500 million smallscale farmers in India and Bangladesh, the annual costs of watershed deforestation in India alone were estimated as far back as the early 1980s at more than $1 billion. A similar decline of watershed services is becoming apparent in the densely populated valleylands of the Irrawaddy, Salween, Chao Phraya and Mekong Rivers in Southeast Asia. Some 40 per cent of developing-world farmers depend upon regular flows of rivers and streams from healthy watersheds to irrigate their croplands.

Then there is siltation of hydropower and irrigation-system reservoirs, deriving in major measure from deforestation in watersheds. The cost is estimated by the World Bank at $6 billion a year. In addition there are the soil conservation benefits of tree cover; within India's forests, these are worth between $5 billion and $12 billion per year, while the nation-wide value of forest services in regulating river flows and containing floods are roughly assessed at $72 billion a year. Perhaps most pertinent of all: what price for watershed services in the year 2025 when a full three billion people in developing countries may well be suffering water shortages?

In addition, deforestation sometimes results in reduced rainfall. In northwestern Peninsular Malaysia, the Penang and Kedah States have experienced disruption of rainfall regimes so large that 20,000 hectares of paddy ricefields have been abandoned and another 72,000 hectares have registered a marked production drop-off in this "rice bowl" of the Peninsula. Similar deforestation-associated changes in rainfall have been documented in much of the Philippines, southwestern India, montane Tanzania, southwestern Ivory Coast, northwestern Costa Rica and the Panama Canal Zone.

Climate links

Still more important is the forests/climate linkage at global level, notably through forests' role as carbon sinks and hence their capacity to mitigate global warming. Forests currently hold some 1200 gigatonnes (billion tonnes) of carbon in their plants and soils (out of 2000 gigatonnes in all terrestrial plants and soils), by contrast with 750 gigatonnes in the atmosphere. Around half of the forest carbon is located in boreal forests, more than one third in tropical forests, and roughly one seventh in temperate forests. Boreal forests, being Earth's largest biome on land, probably contain more carbon than all the Earth's proven fossil fuel reserves. Another way to view the flywheel effect of the world's forests on carbon stocks is to note that they account for 65 per cent of net plant growth and carbon fixation on land. Just Siberia's forests absorb 10 per cent of human emissions of carbon dioxide annually.

© Jorgen Schytte / Still Pictures

When forests are burned - as is the case with cattle ranching and smallscale agriculture in the humid tropics and with fires both wild and human-made in the boreal zone - they release their carbon. Of the roughly 7.6 gigatonnes of carbon dioxide emitted per year into the global atmosphere and contributing almost half of greenhouse-effect processes, 1.6 gigatonnes (plus or minus 0.4 of a gigatonne) come from forest burning in the tropics, almost all the rest stemming from combustion of fossil fuels. All in all, there is a net flux from forests to the atmosphere of 0.9 of a gigatonne (plus or minus 0.4 of a gigatonne) of carbon per year.

© WWF Juan Pratginestos

In addition, global warming itself is expected to cause increased die-off and decomposition of forest biomass, in turn triggering a further release of carbon dioxide. As much as one third of the world's forests could be threatened in this manner.

The largest single tract is in Siberia, amounting to 5.5 million square kilometres or nearly twice as much as in Brazilian Amazonia. Its woody biomass is estimated to contain 40-60 gigatonnes of carbon (though only around half as much as in Amazonia), while its forest soils, detritus and litter contain another two or three times as much carbon (far more than in Amazonia). Since boreal forests are located in northern high latitudes where temperatures will rise most in a greenhouse-affected world, they could soon start to undergo marked desiccation and die-off, aided by the increase in forest fires expected through global warming. Were there to be progressive depletion of boreal forests, their expanse could decline by at least 40 per cent and conceivably 60 per cent within the next three to five decades.

Worse, the incipient decline of boreal forests could well lead to an increased rate of die-off in remaining forests in other parts of the world, plus a decline of biomass in other ecological zones such as grasslands. We could eventually (or even soon) face a "runaway" greenhouse effect as boreal forests decline, taking with them their crucial flywheel function in the global carbon budget.

As for economic evaluation of the stabilizing effect of forests in the global climate system, we can use a "central" value of $20 of global-warming damage for every tonne of carbon released. On this base, carbon storage offers a far higher rate of return than any alternative form of current land use in tropical forests. Alternatively reckoned, to replace the carbon storage function of tropical forests (never mind temperate and boreal forests) could cost as much as $3.7 trillion.

The biggest calculation remains unassessed. If, in fifty years' time, the Earth is largely bereft of its forests, how shall we respond to those descendants who ask how we could afford to watch the terminal reduction of what has been the predominant type of vegetation on the Earth for hundreds of millions of years? Will they not rather ask, "How could you not afford to save the forests in light of all that has been ultimately and irretrievably lost?"

Norman Myers is a Fellow of Green College, Oxford, and a contributing Editor of People & the Planet.