Tropical Infectious and Parasitic Diseases Unit, School of Public Health and Tropical Medicine, James Cook University, Townsville Qld 4811, Australia. Wayne.Melrose@jcu.edu.au.
The nation of Papua New Guinea occupies the eastern half of the island of New Guinea. It lies wholly within the tropics and is centred around 5oS and 145oE. The mean annual rainfall is 2000 mm, and the average temperature exceeds 25oC. Despite the high rainfall, there are often water shortages in Papua New Guinea because the rainfall is seasonal, with about 85% of rainfall occurring in the "wet" season, which can start anywhere between December and May, and range in length from 2 to 4 months. The total land area of PNG is 460,000 sq km and consists of coastal lowlands and a rugged, mountainous interior. The population of PNG is around 4.7 million and is increasing at the rate of 2.5% per year. The most populous area is the highlands with a population density of 18 people per sq km. By contrast, the lowlands have a density of 3 persons per sq km. Eighty five percent of the population live in rural areas but there is increasing urban drift, with people moving to the cities to find work (Attenborough and Alpers, 1992; Papua new Guinea On-Line, 2000). The total forested area of PNG is around 39 million ha out of a total land area of 46.2 million ha. Thirty three million ha is classified as virgin forest, making it the largest stand of such forest on earth (Mullins, 1994). The PNG government has classified 21 million ha as "protected forest" which occupies slopes too steep for logging. Much of the lowland swamp country soils are too poor to support growth of large trees, and the official estimate of productive forests is 18 million ha (Papua New Guinea Information Unit, 1989).
Current estimates of forest destruction are hard to come by, but in the late 1980's forest was being lost at a rate of 21,000 - 22,000 ha per year (Hurst, 1990; Mullins, 1994). Forest product production has increased from 300,000 cubic metres in 1969 to over 1.7 million cubic metres in 1989. Most of these exports are in the form of logs, so Papua New Guinea misses out on any "value added" component that would result if timber were milled locally. Foreign investors, mainly Japanese, Malaysian, Korean, and Chinese, dominate the timber industry. In the late 1980's local timber companies only had rights to one fifth of the available logging concessions (Barry, 2000).
Not everything can be laid at the feet of the logging companies. There are four other causes of forest loss besides logging: shifting agriculture, mining, plantations, and road building. Slash and burn methods are used for traditional agriculture. It is estimated that such practices result in the clearing of 15,000 ha of forest annually. Only a proportion of this however, is virgin forest. Most of the clearing is down on "recycled" land previously cleared for agriculture and subsequently re-grown. Increasing populations in some areas has shortened the fallow time of the land and it is being reused at a rate that is not sustainable, and will result in soil degradation. Simple changes in agricultural practices could make a big difference, for instance, the garden rows traditionally run up and down the hillside. This increases water run off which results in a loss of soil and nutrients. Changing to a horizontal system of rows would conserve water and nutrients. Mining can have a serious effect on the forest. Although large areas of forest are not directly affected by mining, the areas are totally degraded by the open cast system used. Forest clearing for coffee, oil palm, and rubber plantations is increasing in most areas. Road building has caused very little forest loss to the present, but there is expected to be a marked increase in road building during the next decade.
The effects of deforestation on the environment can be classified as direct and indirect (Hurst, 1990; WHO, 1992). Both direct and indirect effects have the potential to impact upon the health of the people.
Except for the highland valleys, and the land along the Fly and Ramu rivers, the soil in PNG is ancient and thin. Erosion readily occurs when the covering vegetation is disturbed. Dr Saulei of the University of Papua New Guinea claims that the timber industry is "accelerating erosion, weathering, and humus decomposition, and leading to widespread formation of soils with low nutrient and absorbent capabilities" (Saulei, 1984). In the Golgol valley, where large areas have been clear felled, the soils have become waterlogged, soil pH has fallen, phosphorus levels have been reduced to 50% of the pre-logging level, and much of the land has become unsuitable for either reforestation or agriculture (Hurst, 1990). Most Papua New Guineans rely heavily upon the gathering of wild food and subsistence agriculture, and a reduction in soil fertility could have a severe impact upon their nutritional status.
The decrease in water absorption increases the amount of run off into the waterways, increases the amount of flooding, and results in an increase in bank erosion. (timber industries are not the only villain in the piece, mining industries must also share the blame). According to Dr. A. Dhal sedimentation damage to coral reefs is becoming a severe problem throughout PNG (Dhal, 1984). The timber industry is only partly to blame, as much of the sediment is the result of opencast mining activity. Fishing is an important food-gathering activity for many coastal people and degrading of the reefs could lead to reduced seafood harvests and a degrading of nutritional status. Papua New Guinea forests are rich in wildlife. Placental mammals, marsupials, birds and reptiles abound. Doubtless there are a lot of species that have not yet come to scientific attention. There are 650 species of birds, 500 of which are confined to the forests (Hurst, 1990). There have been very few studies on the effects of deforestation in PNG wildlife, but judging from the studies done in other rainforest areas of the world, it is likely to be profound. Loss of forest wildlife also means loss of a local food source, and a potential loss of revenue from eco-tourism. The timber industry is not a major polluter of soil and water. Oil spills have occurred from ships and barges employed in the timber trade, the decomposition of sawdust in waterways can cause oxygen depletion. With the move to "value added" downstream processing (which should in fact be encouraged), there is the danger of water and soil pollution by such things as timber preservatives, most of which are very toxic. Water pollution can impact upon health in several ways: ingestion of toxins, ingestion of pathogenic organisms or nutritional depletion due to the loss of food sources such as fish and shellfish.
The tourist industry is only in its infancy in PNG, but the country has tremendous potential as an "eco-tourism" destination. It behooves the country therefore to preserve as much of its natural environment as possible. One obvious example is the area around Mt. Bosavi on the western province, Southern Highlands Province border. This area has virgin rainforest, limestone sinkholes and pillars, and the largest and most scenic waterfall in the country. Despite these attractions, which make it an obvious candidate for a national park, it is under threat from logging.
The area of land, which has been logged in PNG thus far, is too small to influence the local climate, but in South America there have been climate changes due to deforestation. Trees provide a great deal of moisture which influences cloud formation. Ground temperature and the amount of sun-heat reflection vary with the amount and type of vegetation. This in turn has an effect on atmospheric convection currents. As a result of these influences the climate in heavily logged areas become drier and windier (Hurst 1990; Jones 1951). During the last few years Papua New Guinea has suffered a serious drought that has resulted in famine and water shortage. Hundreds of people have died and the health of many survivors has been seriously affected. It is not possible to say how much if any, de-forestation has influenced the severity of the recent drought but if de-forestation continues unabated it is almost certain to cause some degree of climate change in the future.
There is not a lot of data available on the regenerative capacity of the PNG forest. Clear felling, which is now fortunately banned in most areas, has a very detrimental effect on regeneration. Naru Kwapena of the PNG department of Land Survey and Environment says "There is no evidence that the natural tropical forest will regenerate following harvesting of timber.
In fact, the evidence is to the contrary; the forest is effectively destroyed and reduced to very low grade secondary forest with little commercial value" (Kwapena, 1985). Selective logging of mature trees, with minimal damage to surrounding vegetation has much less environmental impact. The author often flies over areas of the PNG forest that have been subjected to both clear felling and selective logging. The clear felled areas are still visible years after logging has ceased. The growth is weak and dominated by weed species. The selectively felled areas, although they will never return to their pristine state, appear to regenerate very quickly and within a few months the jungle is reclaiming even the roads. Logging has important social impacts.
Local landowners can often be induced to offer their land for logging by the promise of financial gain, local infrastructure improvement, and employment and few of them stop to consider the downside of such development. It is Papua New Guinean government policy that the logging companies must provide a certain number of jobs for the local people and must exhaust all possible avenues for the employment of nationals before offering jobs to expatriates. This is a fine ideal but seldom works out in practice. Logging and other forms of industry bring a large number of people from outside the area and often the jobs go to the skilled immigrants rather than the local people.
The wantok system often results in the person who is earning money looking after the less affluent members of the extended family. This means that the number of people flowing into the area is much larger than the number actually required to work in the industry. A single forestry worker and his immediate family may be joined by many relatives and friends who seek to gain off his employment and income. Tension invariably develops from these newcomers and the local people who own the land. The influx of workers and their families means the creation of a town several thousand people where a village of a few hundred or less once stood. This leads to overtaxing of local food and water resources, and increases the problem of the safe disposal of human waste. The rapid increase in population brings with it other social ills. Alcohol is readily available and so is the money to buy it. As a consequence domestic violence, fights, and acts of lawlessness also increase. Prostitution, previously held in check by local cultural taboos, increases and with it, sexual transmitted diseases.
There is much anecdotal evidence to suggest that much of the non-industrial trauma occurring in logging and mining camps is a result of drunken fights over women. Men moving to the logging camps come into contact with women who are more sophisticated and sexually alluring than the simple village girls they may have married and left behind. There are many incidences of such contact causing marriage breakdown and disruption of the family unit. Even if they remain married to their wives, there is the problem of transmission of sexually transmitted diseases to their wives, their babies, and other members of their home community.
Although it is hard to get official statistics on the matter, there is strong anecdotal evidence to suggest that HIV and hepatitis C are on the increase in rural PNG and that some, if not most of these infections, have been transmitted via a male partner who has used prostitutes in urban areas or industrial sites. In a report on the effects of the destruction of the Borneo rain forest on the natives of Sarawak, Dr. Tatsuo Hayashi, records a visit by Dr. Ron Aspinall to the Penan people. He found that sexual diseases increased as the cash economy increased. This was mainly due to Filipino loggers visiting Penan villages in search of women. He also notes that there was an increase in psychological disorders that he blames on the cultural destruction brought about by this destruction of the Penan's forest homeland (Hayashi, 1990). In theory, the local people should gain considerable benefits from logging operations in their area, royalties are paid, and there is income to be earned, both directly by being involved in the operation its self, and by the supply of goods and services.
This should result in an increased cash flow in the local economy and increasing living standards. According to Wood (1985) the direct effect of industry on the economic health of the local population is probably minimal. Wages are very low by international standards, royalties do not reflect the true value of the timber taken, and the real profits are accrued by the logging companies not their employees. It is estimated that with the royalties that were being paid in the 1980's, local land owners had to sell one cubic meter of timber to gain the cost of one small tin of fish - cost about 30 cents (Stewart, 1983). In general, malnutrition is only a problem in Papua New Guinea during periods severe prolonged drought. The staple food in most of the lowland areas is sago, in the highlands it is kaukau (sweet potato), and on the New Guinea islands, taro. Fruits such as banana, pawpaw, pineapples and soursop supplement the staples. Meat is obtained from the hunting of game animals, birds, and reptiles, from domestic animals, or by fishing. In recent years there has been an upsurge in the use of store-brought, processed foods such as tinned fish and rice. In the cities and towns "fast food" is making an impact with such things as lamb flaps, offal, and chicken. The maintenance of traditional food sources is dependent on the preservation of the environment. Most of the game animals are forest dwellers and deforestation seriously reduces their abundance. Pollution of rivers kills fish stocks. Is very important for the health of the people that they have access to traditional food sources. These can be supplemented by store brought food if required. The store-brought foods do have a beneficial effect in that they provide the protein that is lacking in the traditional diet, but if they become the predominant food source, problems may arise. Most of the processed food is high in salt and fat, and fast foods, are usually cooked and served soaked with fat. Hypertension, obesity, kidney disease, heart disease, diabetes, and other "western" diseases, are more common in populations that consume large amounts of these substances. Deforestation has the potential to adversely impact upon health status. Sexually transmitted diseases, and trauma causes by industrial and road accidents, and domestic violence has already been dealt with above. A potentially serious consequence of deforestation is an increase in vector-borne diseases such as malaria, filariasis and arboviral infections (Service, 1991; Bradley, 1993; Walsh et al., 1993; Banerjee, 1996; Molyneaux, 1997, 1998; Gratz, 1999). In most tropical populations, serious malaria is usually seen only in children who have not developed protective immunity. The malaria situation is relatively stable and although there may be seasonable variations in case numbers, epidemics do not usually occur except when stability is disrupted by habitat changes that favor an increase in vectors, establishment of different vectors, and the ingress of infected, or non-immunes, into the area (Walsh et al., 1993). There are three main reasons why logging (and mining) have the potential to increase malarial transmission.
If the vector mosquitoes are forest dwellers it is possible that the clearing of forest can decrease the rate of malarial transmission. De-forestation in Thailand for tapioca farming also destroyed the habitat of the shade lowing vector Anopheles dirus (Bockarie and Paru, 1993). This is the exception rather than the rule and in most places the clearing of land results in an increase in malaria. Those that breed in partially shaded or sunlit water replace the forest-breeding mosquitoes. In some cases these mosquitoes are more efficient vectors those replaced. Forestry practice can result in a massive increase in mosquito breeding sites. Dragging logs through the forest can cause water-filled furrows. Tire marks, hoof prints, and even human footprints, can provide ideal breeding places. Removal of growth along stream edges, slowing of water run off by debris, and impoundment for water supplies, accumulation of coconut shells, tins, tires, and other rubbish, and pooling of water in tree stumps, all increase the breeding potential (Walsh et al., 1993). Clearing of forests in Malaysia for forestry and mining camps led to a marked increase in the numbers of A. maculatis (Bockarie and Paru, 1993). In Sri Lanka clearing land for tea estates led to an increase in the numbers of A. culicifacies and severe epidemics of malaria in areas in which were previously classified as mildly malarious (Jones, 1951; Bockarie and Paru, 1993). Logging and mining have been associated with a massive increase in malaria cases in the Amazon Basin. Cases rose from 5 per 1000 inhabitants in 1971 to 30 per 1000 inhabitants in 1986. In the same period the proportion of Plasmodium falciparum (the most severe form of malaria) cases increased from 45% to 85%. Although habitat modification played a role, the telling factor was migration. Migrants brought with them strains of malaria to which the local population, and many of the migrants, had no immunity (Cruz Marques, 1987). Malarial outbreaks have a large economic impact on the financial viability of the mining and logging operations. At one mine, a 12% reduction in income occurred due to absenteeism, and profits for the company were reduced by the same amount (Vosti, 1990). Many species of mosquitoes prefer to feed on animals rather than humans. Destruction of animal habitats, and a decline in the number of wild animals forces the mosquitoes to feed on domestic animals and humans. The frequency of human feeding has a marked influence on malarial transmission.
In 1975, a PNG government entomologist, Dr. Margaret Spencer (Spenser, 1975), drew attention to the probable increase in malarial mosquito breeding due to forest clearing. She writes: "There is no doubt that forest clearing will increase the breeding potential for malarial mosquito vectors in the Golgol area or northern Papua New Guinea, largely by creating man-made breeding places. These will be many and various, e.g. standing water left in holes caused by up-rooted tree stumps, in bulldozer and other tracks, wheel ruts, and roadside ditches, ruts caused by dragging of logs, and blocking of roadside drainage.” In heavily forested inland areas of Papua New Guinea the main malarial vector is Anopheles koliensis, which breeds in semi-permanent water at the forest margin. In the opinion of Moses Bockarie and Raymond Paru from the Papua New Guinea Institute of Medical Research, destruction of the forest can result in A. koliensis being replaced by A. punctulatis which is an important malarial vector that breeds in small sunlit collections of water and is a more efficient vector than A. koliensis. In a survey of 76 sites in the Western province A. punctulatis was only found at a refugee camp where forest had be cleared to accommodate the camp (Bockarie and Paru, 1993).
In some instances forest clearing and replacement with another type of vegetation can reduce transmission. Chang et al. (1997) report that the clearing of forest and replacement with oil palm plantations decreased the number of malaria-transmitting Anopheles mosquitoes and thereby reduced the threat of malaria transmission by 90% over a 4 year period. Unfortunately this success was tempered by an increase in dengue fever-transmitting mosquitoes, which Chang et al. refer to as “the law of unintended consequences.” The clearing of forest for a new international airport in southern Cameroon caused an increase in malaria transmission due to increased vector breeding in the cleared area (Manga et al., 1995).
Much of the foregoing discussion on malaria also applies to lymphatic filariasis, a mosquito-borne parasitic disease, which in its extreme form can cause the terrible disfiguring disease elephantiasis. Due to the large number of mosquito species that spread filariasis and their varying breeding habitat requirements, deforestation can result in a reduction or an increase the transmission of lymphatic filariasis. In Thailand, the filarial parasite Wuchereria bancrofti is transmitted by Aedes niveus, a forest breeder, and forest clearing has reduced the incidence of transmission (Walsh et al., 1993). In parts of Malaysia the filarial species Brugia malayi occurs in monkeys. The same has occurred in parts of Malaysia and Borneo, where Brugia malay occurs the natural reservoir is the monkey population and is transmitted to humans by Mansonia mosquitoes which breed in forest swamps. Deforestation reduces the number of reservoir animals and destroys breeding sites and for some years the incidence of Brugia malayi infections decreased. In recent years however, infections have increased in Malaysian rubber estates because the monkeys that have lost their forest habitat, have moved closer to human habitation in search of food (Walsh et al., 1993). In the hilly parts of Malaysia, there has been an increase in the transmission of W. bancrofti-induced filariasis transmission when forests have been cleared and breeding habitat for the most prominent vector, A. maculatus has increased (Cheong, 1983). In Papua New Guinea, lymphatic filariasis is transmitted by A. punculatis, Mansonia species, and Culex species. Mansonia tends to be a forest breeder, but A. punctulatis as noted above favors sunlit water. Culex tends to frequent areas of human habitation and likes to breed in polluted water, such as abandoned water-filled toilets, or water contaminated by human or animal feces and forest clearing and urbanization has the potential to change the transmission potential of lymphatic filariasis.
Of the 520 known arboviruses, 100 cause human disease. Animals are the normal reservoirs of arboviruses and many of the human diseases caused by them are zoonoses. Arbovirus disease increases when man's activities cause gross disturbance to pristine environments, which brings may into close proximity to animal hosts and vectors (Fienes, 1978; Walsh et al., 1993). The effect of human migration and habitat modification on arbovirus disease is dramatically portrayed by looking at its effects on Kyasanur Forest Disease, a tick-borne arbovirus disease discovered in India in 1957 (Walsh et al., 1993; Banerjee, 1996). When first discovered the disease was confined to a very localized area. The disease quickly moved outwards from its local focus and by 1966 was endemic across an area of 1300 km2. The number of cases rose from 75 cases in 1957 to 1555 cases in 1983. The reason for the spread of disease and increased cases was due to human migration and habitat modification. Groups of people and cattle moved into the forest to be close to fuel-wood. Trees were cut down to provide the fuel-wood, to make room for housing, and to provide grazing for the cattle. Nomadic behavior resulted in the cleared areas experiencing profuse growth of lantana vine. This vine grows rapidly in second-growth forest and clearings. The vine thickets provide the ideal habitat for small mammals and birds, which act as hosts for immature ticks. Cattle were left to graze in the forest by day, where they picked up ticks, and were tethered close to houses, or in houses at night where ticks could transfer to human hosts. Humans also picked up ticks when they entered the forest to collect wood, or clear land for new settlements.
Dengue, Ross River, Murray Valley Encephalitis, Kunjin, Barmah Forest and Japanese Encephalitis viruses are known to be present in Papua New Guinea (Trevett and Sanders, 1994; Mackenzie et al., 1994; Johansen et al., 1997). It is certainly possible that an increase in mosquito breeding habitat due to forest clearing and the associated increase in human settlement could increase the prevalence of arbovirus disease.
Deforestation can also exert an effect on diseases transmitted primarily by fecal contamination of drinking water such as bacterial, cryptosporidial, amoebic, and helminth bowel infections, and hepatitis A. Lilly et al. (1997) reported an increase in hookworm infection when flooding caused by deforestation-associated river silting produced soil changes that facilitated the transmission of the parasite. Population increases near logging facilities and the consequent increase in human waste, increases the risks of fecal contamination of water supplies and an increase in water-borne disease.
Most of the foregoing may seem essentially negative but the purpose of this document is to sound a warning about possible adverse effects of logging in the Papua New Guinea rainforest. The best solution would be complete preservation of the rainforest forever, but one has to be realistic. If Papua New Guinea is to grow as a nation, have a vibrant economy, and provide adequate health care and education for its growing population, it must make use of its natural resources. The timber industry will continue to play an important part in the countries future, but unless the resource is handles in a wise way, and the adverse impact of logging upon the human population is minimized, it will be a case of killing the goose that laid the golden egg. Areas of forest should be set-aside as wilderness areas and national parks. Ecotourism in the rainforest should be explored as an alternative to logging and if logging does take place it must be done in a sustainable manner, using management practices that have minimal environmental impact.
It is now becoming increasingly apparent that clear felling has no place in rainforest management, and that the only harvesting permitted should be of selected mature trees, with minimal disturbance of the surrounding jungle. Mosquito breeding must be discouraged by providing adequate drainage and standing water should be treated with larvicides. The economic, social, and spiritual needs of the people gathered in logging settlements must be addressed early and adequate infrastructure put in place to provide, housing, clean water, food supply, waste disposal, health care, and recreational facilities.
The real key to environmental protection however is education. To many Papua New Guineans, the only way to gain social and financial advancement is to exploit their natural resources. They can hardly wait for "the company" to come, because the company, almost considered a demigod, will provide jobs, money, and material goods. Many of the people however, especially the more educated young, are beginning to realize the folly of allowing the rape of the natural environment. In recent years there has been increasing protests about logging and mining activity, and national people have begun to take the multinational companies to task over their environmental record (Wood, 1985). Local people are realizing the value of their forests and many groups are supporting a moratorium on large-scale logging in favor of sustainable, village-based eco-forestry. This call is also being supported by a increasing number of people within the political system (Barry, 2000).
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