BOOK REVIEW

Book Reviewed in this article:
A Place Against Time–Land and Environment in the Papua New Guinea Highlands By P. Sillitoe.     

The crocodile project in Papua New Guinea

Crocodilians throughout the world are under very heavy pressure from habitat destruction, human displacement and deliberate hunting for skins. In Papua New Guinea crocodiles of two species are still relatively plentiful and play an important part in the economy of many remote settlements. An attempt is being made by the national government to implement a policy intended to bring about the harvesting of wild crocodiles on a sustained yield basis and provide an economic incentive for conserving wild stocks in their natural habitat. Low human population density and the existence of vast swamplands make this a possibility. In recognition of the policy and the exceptional circumstances, Papua New Guinea has been exempted from trade restrictions imposed by a number of countries under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).     

Soil-landform relationships at two localities in Papua New Guinea

Two test areas, each of several hectares, in denudational terrain in the lowlands and highlands of Papua New Guinea were intensively studied to establish the association between soil conditions and landforms. Whether soils were allocated either to the great soil groups of a classification based on the 7th Approximation or to FAO soil units, an extremely wide range of soils occurred in each of the land units that could be distinguished on the basis of landform. Defensible statements concerning soil distribution were achieved only by limiting the categories of soil to the level of soil orders and by restricting the number of land units to three or four. Even so, the statistical significance of the relationships was very low.These results indicate that current techniques and sampling densities used in photointerpretative land resource surveys in terrains typical of Papua New Guinea can produce only very generalized information on soil distribution. To obtain reliable predictions of soil information at the level commonly implied in such surveys, further intensive studies on the relationships between attributes of soil, landform and vegetation are required.     

Demonstrating decline of an iconic species under sustained indigenous harvest – The pig-nosed turtle (Carettochelys insculpta) in Papua New Guinea

Papua New Guinea has astonishing biological and cultural diversity which, coupled with a strong community reliance on the land and its biota for subsistence, add complexity to monitoring and conservation and in particular, the demonstration of declines in wildlife populations. Many species of concern are long-lived which provides additional challenges for conservation. We provide, for the first time, concrete evidence of a substantive decline in populations of the pig-nosed turtle (Carettochelys insculpta); an important source of protein for local communities. Our study combined matched village and market surveys separated by 30 years, trends in nesting female size, and assessment of levels and efficacy of harvest, each of which was an essential ingredient to making a definitive assessment of population trends. Opportunities for an effective response by local communities to these declines needs to consider both conservation and fisheries perspectives because local communities consider the turtle a food resource, whereas the broader global community views it as a high priority for conservation. Our study in the Kikori region is representative of harvest regimes in most rivers within the range of the species in Papua New Guinea, and provides lessons for conservation of many other wildlife species subject to harvest.     

Influence of water level,hunting pressure and habitat type on crocodile abundance in the fly river drainage,Papua New Guinea

Between October 1978 and July 1980, day and night crocodile surveys were conducted at low, normal and high water levels over 2703 km of river and lakeshore in the Western and Southern Highlands provinces of Papua New Guinea. The 1353 crocodiles seen ranged between 0·18 and 2·23 animals per km.Night counts recorded 12·9 times as many crocodiles as day counts over the same area. This may indicate more nocturnal activity than occurs in other crocodilians. Unhunted areas had a greater proportion of large crocodiles than did hunted regions. As the water level rose, the ‘visible juveniles’ category decreased as a result of migration into newly flooded adjacent swamplands. The upstream range of New Guinea crocodiles on the Strickland River extended only to the Burnett River junction.There was an increase in flight distance with increasing body size and this rate of increase was over twice as large for hunted populations as for unhunted ones.     

Trace element concentrations in tropical marine fish at Bougainville Island,Papua New Guinea

Baseline trace element concentrations have been measured in eight species of marine fish from Bougainville Island, Papua New Guinea. This is the first stage in an assessment of environmental impact associated with mining operations. In general, concentrations of Cu, Pb, Zn, Cd, Hg, and As in edible portions of the fish comply with Australian National Health and Medical Research Council public health standards. Two species of shark contained As concentrations in muscle tissue in excess of prescribed standards. Increased concentrations of Cu, Zn, and Cd were recorded in liver and kidney, but Hg and Pb were not preferentially accumulated in these organs. The relationship between the size of fish and metal assay was investigated. Mercury content and weight of fish were always positively correlated but concentrations of other metals were variably correlated with size.     

The introduced fishes of Papua New Guinea with special reference to Tilapia mossambica

Twenty-one species of freshwater fishes in 19 genera (Salmo, Salvelinus, Retropinna, Barbus, Ctenopharyngodon, Cyprinus, Hypophthalmichthys, Puntius, Tandanus, Gambusia, Poecilia, Percolates, Plectroplites, Bidyanus, Tilapia, Trachystoma, Hypseleotris, Osphronemus and Trichogaster) representing 11 families and all six continental regions have been introduced into Papua New Guinea. A list of species, date of first introduction, distribution and comments are presented. The dispersal of Tilapia mossambica on Bougainville Island from a single introduction followed by floods and human transport is discussed.     

RAPD variation in sweetpotato (Ipomoea batatas (L.) Lam) cultivars from South America and Papua New Guinea

The island of New Guinea is considered a secondary center on diversity for sweetpotato, because of its range of isolated ecological niches and large number of cultivars found within a small area. Information of genetic diversity in Papua New Guinea (PNG) sweetpotato is essential for rationalizing the global sweetpotato germplasm collection. Using random amplified polymorphic DNA (RAPD), we compared the genetic variation and genetic diversity in 18 PNG cultivars versus 18 cultivars from South America. The analysis of molecular variance revealed large genetic diversity in both groups of cultivars. The within-group (among individuals) variation accounted for 90.6% of the total molecular variance. However, the difference between PNG and South American groups is statistically significant, although it explained only 9.4% of the total molecular variance. The PNG cultivars are also less divergent than their South American ancestors as the mean genetic distance in PNG group is significantly smaller than that of South American group. The lower level of genetic diversity in PNG cultivars was also reflected by multidimensional scaling. This study shows that PNG cultivars, after many years of isolated evolution in an unique agro-ecological environment are substantially divergent from their ancestors in South America. The genetic diversity level in PNG cultivars is significantly lower than that in South American cultivars. It thus provides a baseline for continuing studies of genetic diversity in different sweetpotato gene pools.     

Biochars influence sweet‐potato yield and nutrient uptake in tropical Papua New Guinea

Currently, the biomass of an invasive and obnoxious weed, kunai grass (Imperata cylindrica), is uncontrollably burnt in Papua New Guinea in subsistence farming systems resulting in unwarranted negative environmental consequences. We explored the possibility of sustainable utilization of biochar produced from the weed biomass along with a standard feedstock‐rice husk (Oryza sativa). Biochars were produced with lab‐scale pyrolysis at 550°C, characterized for chemical properties and plant nutrient composition. Further, agronomic efficacy of soil incorporation of biochars (5 t ha^?1) or co‐applied with mineral fertilizers (100, 11, and 62 kg ha^?1 N, P, K, respectively) was tested for sweet potato (Ipomoea batatas L. Lam) in a field experiment. The two biochars differed significantly (P < 5%) with respect to recovery from the feedstocks, chemical characters and nutrient composition. Kunai grass biochar was poorer in nutrients (< 1%) with distinctly alkaline pH and higher electrical conductivity. Biochar amendment to soil showed significant (P < 5%) improvement of soil moisture, while co‐application of biochars along with mineral fertilizers showed soil moisture decrease. Biochar amendment improved the growth parameters and total tuber yield of sweet potato by about 20%, while co‐application with mineral fertilizers augmented total tuber yield by 100% and above‐ground biomass yields by > 75%. Besides, improving agronomic performance of sweet potato crop, co‐application of biochars with mineral fertilizers enhanced uptake of N, P, K, Ca, Mg, and S. Production and utilization of biochar in sweet‐potato production could offer an efficient means of disposing biomass of kunai grass with concomitant productivity improvement in Papua New Guinea.     

Sustainability of hunting, population densities, intrinsic rates of increase and conservation of Papua New Guinean mammals: A quantitative review

New Guinea’s mammalian fauna consists of a unique assemblage of relatively small sized (0.5-13.5 kg) marsupial mammals, the hunting of which provides a major source of protein for local communities. However, the impact of hunting and the influence of the marsupial life-history strategies on the sustainability of hunting are unknown. Anthropological studies of subsistence hunting and published life-history data for Australasian marsupial mammals were quantitatively reviewed to determine the major sources of game and annual harvest, and estimate intrinsic rates of population increase (r_max) and population densities. These data were used to estimate extraction versus maximum sustainable production (MSP) and make a preliminary estimate of the sustainability of hunting. There were significant negative relationships between increasing body size and decreasing r_max and decreasing population densities, which were further influenced by phylogeny and diet, and appear very similar to relationships found for placental mammals in Afrotropical and Neotropical forests. The estimated biomass of mid-sized marsupial mammals (923 kg/km²) in Papua New Guinea is also comparable with densities of placental mammals in other evergreen tropical forests. Intrinsic rates of increase ranged from 0.28 for tree-kangaroos (Macropodidae) and 0.29 for cuscus (Phalangeridae), up to 5.14 for bandicoots/echymipera (Peroryctidae). Estimated population densities ranged from 0.4-4.0 animals/km² for long-beaked echidna (Zaglossus sp.) to 150-340 animals/km² for ringtails (Pseudocheridae). Extraction rates of game in three studies averaged 23.5 ± 9.9 kg/km²/year, with cuscus and bandicoot species numerically comprising the main game, although cuscus are the most important source of protein. Rates of extraction in Papua New Guinea versus rates of production demonstrate that long-beaked echidna, tree-kangaroos and cuscus are likely to be hunted unsustainably. In contrast hunting of bandicoots and ringtails was lower than maximum production levels, and the high intrinsic rate of increase of bandicoots means that they can potentially provide a sustainable source of protein, in preference to scarcer and intrinsically slower breeding species.     

Soil fertility under shifting and semi-continuous cultivation in the Southern Highlands of Papua New Guinea

Abstract. People in the Southern Highlands of Papua New Guinea cultivate some land semi-continuously within a regime of shifting cultivation; the staple crop is sweet potato ( Ipomoea batatas ). The fertility of Tropepts, variably affected by falls of volcanic ash, was investigated to give further understanding of how subsistence farmers avoid the soil constraints that commonly prompt abandonment. While organic matter, N and K all decrease significantly with time under cultivation, they do not reach critical levels. Phosphorus also decreases significantly over time, although contents are small throughout. Other nutrients show no significant variation with period of use or abandonment. These findings comply with the diversity of crops cultivated early in the life of 'gardens', followed by sweet potato, cultivated as a virtual monocrop in long established 'gardens'. It continues yielding adequately regardless of decrease in nutrient availabilities, notably because nutrient ratios remain favourable for tuberisation and because of sweet potato's tolerance of small phosphorus concentrations. It appears that burning of vegetation significantly increases available minerals and helps maintain a supply which is adequate for longterm sweet potato monoculture. Similar situations are postulated for other areas of less-weathered soils within the tropics.     

The trade in fruit bats Pteropus spp. on Guam and other Pacific islands

Residents of Guam, Mariana Islands, have imported large numbers of fruit bats Pteropus spp. from other Pacific islands during the past 10 years as a delicacy. The trade in bats began in the 1960s or early 1970s after overhunting had greatly reduced the populations of Guam's native fruit bats. The quantity of bats shipped to the island peaked in 1979 and 1980, with an estimated total of more than 24 000 animals brought in each year. From 1981 to 1984, imports fell to an estimated mean of 14 475 bats per year. During the 1970s, Guam's importers purchased bats mainly from the Caroline Islands (Palau and Yap) and other islands in the Marianas (Saipan, Rota and Tinian). Changes in availability and laws during the 1980s have caused the fruit bat trade to expand geographically, making islands outside Micronesia (Western Samoa, Tonga, American Samoa and Papua New Guinea) important suppliers of bats. Because large-scale commercial exploitation may severely deplete an island's population of fruit bats, perhaps beyond the point of recovery, we recommend that island governments be conservative in the number of bats allowed for harvest until studies on abundance and life history have been completed.     

Knowing the land: soil and land resource evaluation and indigenous knowledge

Abstract. Scientific land and soil resource surveys have had only limited impacts locally on development and extension practice in the tropics. They are thought to have little relevance for subsistence farmers. Their failure to accommodate local social and cultural priorities is a factor. Soil scientists have, until recently, given little attention to others' understanding of soil or 'ethnopedology'. The incorporation of indigenous soil and land resource knowledge has recently been advocated to improve their relevance. But a common error is uncritically to impose a western scientific model, which may distort understanding. The ill-informed, decontextualised knowledge that results may even promote negative interventions. This paper criticises the narrow idea of 'indigenous technical knowledge', citing evidence from Papua New Guinea, Bangladesh and Indonesia. While we find farmers consistently use some of the same information as scientists to assess soils, their definitions of soils and land types are often at odds. Scientists identify classes by a range of technically assessed properties, whereas farmers may not. Their more holistic approach also accounts in part for the disjunction, frequently incorporating exotic social and cultural aspects. The wider use of indigenous soil notions in agrotechnology transfer may be limited too by some of their intrinsic characteristics, inclined to be location specific, and culturally relative.     

Losing ground? soil loss and erosion in the highlands of papua new guinea

First impressions suggest that the risk of soil loss through fluvial erosion from land under cultivation is considerable in the Southern Highlands Province of Papua New Guinea. the climate is very wet all year round, The terrain precipitous, and people regularly farm on steep slopes. the Wola-speaking people, who occupy a series of valleys in the centre of the province, and who practice a semi-shifting form of cultivation, are nonetheless off-hand about soil conservation and declare that erosion is not a serious problem. This paper assesses the status of their assertions by calculating potential soil loss rates. It applies the universal soil loss equation to data on rainfall erosivity, soil erodibility, slope length and steepness, vegetation cover and conservation measures, to compute likely runoff losses. the calculations suggest that, The steep slopes cultivated and wet climate notwithstanding, The local population's assessment of the dangers of erosion is realistic and not reckless. Although rainfall is high, it is rarely of an intensity sufficient to threaten serious soil erosion losses. the physical properties of the soils, which feature volcanic ash components and high organic matter levels, are such that they are particularly resistant to erosion. the staple crop of the region, sweet potato (Ipomoea batatas), also gives particularly good ground cover and protection when established, effectively shielding the soil from erosive rainfall.