The Ecological Component of Environmental Impact Assessment: A Critical Review of British Environmental Statements

Environmental assessment (EA) of the impacts of development is required under the 1985 European Directive 85/337/EEC, which is implemented in Britain primarily through the 1988 Town and Country Planning (Assessmentof Environmental Effects) Regulations. Ecology provides analytical procedures for studying relationships between organisms and their environment and therefore has an obvious role in EA. The status of ecology within the British EA process was investigated by analysing 179 environmental statements (ESs) produced between 1988 and 1993. In many cases, the ecological information provided was so limited in quantity, or of such poor quality, that it was not possible to assess the ecological implications of proposed schemes. Many ESs failed to provide the data necessary to predict ecological impacts. Potential ecological impacts were reported in 93% of statements, but only 9% made any attempt to quantify them. Of those ESs which made references to ecological effects, only 45% based their findings on new ecological survey information. Consultation with statutory consultees for nature conservation was reported in 48% of ESs. Although 78% of ESs mentioned mitigation measures, only 23% described them in detail. A major shortcoming was the universal failure to make any commitment to monitoring of development impacts. In addition to the lack of formal requirements for monitoring, the lack of guidance for ecologists and developers involved in EA is concluded to be a major factor behind some of the shortcomings summarized in this paper.     

Field demonstration of the combined effects of absorption and evapotranspiration on septic system drainfield capacity.

Drainfields for disposal of septic tank effluents are typically designed by considering the loss of water by either upward evapotranspiration into the atmosphere or lateral and downward absorption into the adjacent soil. While this approach is appropriate for evapotranspiration systems, absorption systems allow water loss by both mechanisms. It was proposed that, in areas where high evapotranspiration rates coincide with permeable soils, drainfield sizes could be substantially reduced by accounting for both mechanisms. A two-year field demonstration was conducted to determine appropriate design criteria for areas typical of the Texas High Plains. The study consisted of evaluating the long-term acceptance rates for three different drainfield configurations: evapotranspiration only, absorption only, and combined conditions. A second field demonstration repeated the experiments for additional observation of the combined evapotranspiration and absorption and achieved similar results as the first study. The field tests indicated that the current design loading criteria may be increased by at least a factor of two for the Texas High Plains region and other Texas areas with similar soil composition and evapotranspiration rates, while still retaining a factor of safety of two.     

Household Willingness to Pay and Farmers' Willingness to Accept Compensation for Establishing a Recreational Woodland

The UK Forestry Commission's recently implemented Community Woodland scheme sets out to provide new recreational woodland facilities near to towns and cities where such resources are in short supply. This study examines household willingness to pay (WTP) for such a proposed woodland by means of the contingent valuation (CV) method. A stratified sample of 325 households in Wantage, Oxfordshire, was interviewed and asked to state both their annual and per-visit WTP. Analysis of a number of recognized potential biases suggested that the results obtained must be treated with caution although we argue that the CV provides a useful ballpark indication of preferences. A simultaneous CV survey of farmers' willingness to accept compensation for converting agricultural land into woodland proved to be far more robust, despite a small sample size. We conclude that farmers are more familiar with the concept of assessing potential compensation than are households with estimating hypothetical payments for increased provision of public goods.     

Hereditary Blindness in a Captive Wolf (Canis lupus) Population: Frequency Reduction of a Deleterious Allele in Relation to Gene Conservation

Numerous cases of hereditary diseases and disorders have been reported in wild animals bred in captivity, but little attention has been paid to the particular genetic management problems that arise when such defects occur. These problems include the obstacle of eliminating the deleterious allele(s) without contemporary loss of genetic variability. In this paper we use the statistical methods of pedigree analysis to address questions regarding a previously presumed hereditary form of blindness observed in a captive wolf population bred for conservation purposes in Scandinavian zoos. The most likely mode of inheritance coincides with an autosomal recessive allele with either a full penetrance or a reduced penetrance of 0.6 (depending on the reliability of studbook records). Using these two models of inheritance, we calculate the probability of carrying the blindness allele for each living animal. Analysis of the effect of removing high-probability carriers on founder allele survival and level of inbreeding demonstrates that the frequency of the deleterious allele can be significantly reduced without seriously affecting founder allele survival or current degree of inbreeding in the wolf population.     

Comparative Toxicities of Polar and Non-Polar Organic Fractions From Sediments Affected By the Exxon Valdez Oil Spill in Prince William Sound, Alaska

Standardized tests were applied to aromatic and polar fractions of sediment extracts to determine whether polar constituents or oxidative degradation products contributed significantly to the toxicity of sediments oiled by the Exxon Valdez spill. Intertidal sediment and pore-water samples were collected in September 1990 from two heavily oiled sites and an unoiled site in Prince William Sound (PWS). Methylene chloride extracts from these samples were fractionated by liquid chromatography into aliphatic, aromatic and polar fractions, and the aromatic and polar fractions were tested for toxicity using the Microtox^R test, bivalve larval mortality and development (Mytilus); several measures of genotoxicity in Mytilus, including SOS Chromotest^R, anaphase aberrations and sister chromatid exchange; and survival, anaphase aberrations and teratogenicity in coho salmon (Onchorhynchus kisutch). Microtox^R and SOS Chromotest^R protocols were applied in a screening mode to all samples, whereas other tests were applied only to selected fractions from two sites. Samples from Bay of Isles (oiled) were consistently more toxic (usually only 2 to 5-fold) than the Mooselips Bay (unoiled) samples, which gave very low responses in all tests. for both sites, however, responses to polar and aromatic fractions were about the same in most tests, suggesting that while the overall toxicity of the oil was low in these samples, at least part of that toxicity was derived from polar constituents. Compared to the parent hydrocarbons, polar oxidation products partition preferentially into pore-water and are more rapidly diluted and dispersed in the water column. These results suggest that polar oxidation products of petroleum hydrocarbons pose little risk to marine organisms, except possibly for infauna continuously exposed to pore-water in heavily oiled sediments. Independent surveys showed that sediment toxicity in PWS declined during 1989-1991 to near background levels, in accord with previous understanding of oil weathering and toxicity.     

New Approaches Toward a Better Understanding of the Decline of Takahe (Porphyrio mantelli) in New Zealand

Island populations of endemic birds are known to be particularly susceptible to extinction. This paper focuses on factors behind past and present declines of the highly endangered Takahe ( Porphyrio mantelli ), a flightless rail endemic to New Zealand. Subfossil evidence indicates that Takahe were once found throughout this island nation, being most abundant along forest margins and streams in lowland regions. Their numbers have declined dramatically since human colonization about 800–1000 years ago, probably due to a combination of habitat destruction and hunting by early Polynesian settlers. Today, the wild Takahe population consists of about 100 adult birds in an isolated alpine habitat and approximately 30 individuals recently released on several small offshore islands. Despite protection and intensive management, including removal of an introduced competitor (red deer, Cervus elaphus ), the alpine population has continued to decline. In contrast, the Takahe's nearest relative, the Pukeko ( Porphyrio porphyrio ) has expanded its range across New Zealand despite heavy hunting pressure since its colonization from Australia less than 1000 years ago. We suggest that, unlike Pukeko, Takahe lack appropriate behavioral responses to cope with mammalian predators such as stoats ( Mustela erminea ), which have been introduced relatively recently by European colonists. A study comparing predator defense behavior between these two closely related species is currently underway.