Natural ecosystems

Several recent expert reviews and workshops have discussed the effects of endocrine disruption on wildlife and especially invertebrate species. These include the EU workshop on the impact of endocrine disrupters on human health and wildlife (Weybridge, 1996), the lEH workshop (Leicester, May 1997), the Environment Agency Consultative report (January 1998) and the Tyndall Forum at the Royal Institution (February 1998). They have concluded that endocrine disruption may have far-reaching adverse consequences for biodiversity and the sustainability of natural ecosystems. More comprehensive bioassay systems are required to identify and assess chemicals alleged to produce endocrine modulating effects. 

Has a world-wide database of federal and non-profit environmental research organizations that focus on the multiple aspects of global environmental change, including the regional effects on natural ecosystems, environments and resources as well as on human health, culture and social systems. 

From this analysis it is clear that in addition to their benefits, the use of pesticides in food production not only causes serious public health problems but also considerable damage to vital agricultural and natural ecosystems in the United States and world. A conservative estimate suggests that the environmental and social costs of pesticide use in the United States total about 4 billion each year. Worldwide the yearly environmental and public health costs are probably at least 100 billion. This is several times the 18 bllllon/yr spent on pesticides in the world. 

Bazzaz, F. A. (1990). The response of natural ecosystems to the rising CO2 levels. Annu. Rev. Ecol. System. 21,167-196. 

The possible effects of increased atmospheric CO2 on photosynthesis are reviewed by Goud-riaan and Ajtay (1979) and Rosenberg (1981). Increasing CO2 in a controlled environment (i.e., greenhouse) increases the assimilation rate of some plants, however, the anthropogenic fertilization of the atmosphere with CO2 is probably unable to induce much of this effect since most plants in natural ecosystems are growth limited by other environmental factors, notably light, temperature, water, and nutrients. 

Granhall, U. (1981). Biological nitrogen fixation in relation to environmental factors and functioning of natural ecosystems. In "Terrestrial Nitrogen Cycles" (F. E. Clark and T. Rosswall, eds). Ecological Bulletin 33, 131-145. Swedish Natural Science Research Council, Stockholm. 

Table 12.1. Diec-lissue differences iri 5 N CA N) in controlled diet experiments and within modern natural ecosystems.

Ivanovici, A.M. Wiebe, W.J. (1981). Towards a working definition of stress A review and critique. In Stress Effects on Natural Ecosystems, ed. G. W. Barrett R. Rosenberg, pp. 13-27. New York Wiley. 

Ek osystem recovery from environmental extremes The examples which illustrated the responses of agricultural ecosystems to extreme events have been limited to short-term effects on productivity. For natural ecosystems which can not be replanted the recovery response to an environmental extreme is crucial, not only in the time taken for recovery but also in terms of the manner in which the ecosystem may change during and after the period of recovery. In this context, change is particularly concerned with the species which constitute an ecosystem, a consideration which is central to the aims of conservation. 

Catastrophic breakdown of ecosystems can also be observed in natural ecosystems, without the influence of alien species. One such global problem is forest dieback (Mueller-Dombois, 1986), which is occurring over the globe without obvious cause. Hosking Hutcheson (1986) have made observation on dieback in the evergreen broadleaved forests of New... 

It has been shown that a combination of photolytic and biotic reactions can result in enhanced degradation of xenobiotics in municipal treatment systems, for example, of chlorophenols (Miller et al. 1988a) and benzo[a]pyrene (Miller et al. 1988b). Two examples illustrate the success of a combination of microbial and photochemical reactions in accomplishing the degradation of widely different xenobiotics in natural ecosystems. Both of them involved marine bacteria, and it therefore seems plausible to assume that such processes might be especially important in warm-water marine enviromnents. 

Organisms in natural ecosystems may not be actively dividing but may, nonetheless, be metabolically active. This may be particularly important for ultramicro marine bacteria in their natural habitat. 

Results from experiments on biodegradation in which readily degraded substrates such as glucose are added have probably restricted relevance to natural ecosystems in which such substrates exist in negligible concentration. However, readily degraded substrates in addition to those less readily degradable undoubtedly occur in biological-waste-treatment systems. In these circumstances, at least three broadly different metabolic situations may exist ... 

In natural ecosystems, microbial growth and metabolism may be limited by the concentrations of inorganic nutrients such as nitrogen, phosphorus, or even iron. Systematic investigation of these... 

Plasmid transmission and the stability of plasmids in natural ecosystems have received considerable attention, but caution should be exercised in drawing general conclusions on the basis of the sometimes fragmentary evidence from laboratory experiments. Some important principles are illustrated by the following ... 

It has been shown (Smith et al. 1978) that in enteric bacteria carrying thermosensitive plasmids coding for the utilization of citrate and for resistance to antibiotics, rates of transmission were negligible at 37°C but appreciable at 23°C—a temperature more closely approaching that which prevails in natural ecosystems. 

Input rates of organic C into the soil system are hard to quantify, particularly for natural ecosystems and to a lesser extent for agricultural ecosystems. Whereas quantity and quality of carbon inputs via litter fall and plant residues after harvest might be directly measurable, inputs via roots and rhizodeposition are more difficult to assess. 

These DNA markers have been successfully employed to track specific strain-associated loci in endo- and ectomycorrhizal populations from agricultural land, forest nurseries, plantations, and natural ecosystems. The simplest strategy (digesting PCR-amplified ITS with selected endonucleases) has identified their symbionts in various ecosystems (18,36-38). Species discrimination by ITS-RFLP matching can be improved by comparing data for the targeted DNA with those on sequence databases (37). 

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