Sensitivity of ecosystem

Kuylenstierna J. C. I. and Chadwick M. J. (1989) The relative sensitivity of ecosystems in Europe to the indirect effects of acidic depositions. In Regional Acidification Models (eds. J. Kamari, D. F. Brakke, A. Jenkins, and R. F. Wright). Springer, Berlin, pp. 3-22. 

Based on the mineralogy controlling weathering and soil development, sensitivity of ecosystem to acid deposition is assessed with a comprehensive consideration on the effect of temperature, soil texture, land use and precipitation. The results show that the most sensitive area to acid deposition in China is Podzolic soil zone in the Northeast, then followed by Latosol, Dark Brown Forest soil and Black soil zones. The less sensitive area is Ferralsol and Yellow-Brown Earth zone in the Southeast, and the least sensitive areas are mainly referred to as Xerosol zone in the Northwest,... 

The maps for CL of sulfur derived from this methodology have been overlaid with current (or projected future) deposition maps in order to show areas where the CL of sulfur is (or will be) exceeded. In order to manipulate with the numerous maps and data a geographical information system (CIS) was used (Kozlov and Towprayoon, 1998). As a result of both the high sensitivity of ecosystems and level of exceedances across Northern Thailand, more than 75% of the ecosystems across about 50% of this territory is at significant risk from acid deposition. 

There is good evidence that recent man-induced environmental and climate change is having a noticeable effect on the physical circulation and on the biogeochemistry of this most sensitive of ecosystems that will be discussed at the end of this chapter. 

Modern studies have already documented the occurrence of acid rains over Northern Thailand due to the increase in use of lignite as an energy source. Based on the critical load concept, Kozlov Towprayoon (1998) have shown that the critical load values of sulfur for terrestrial Tropical Rain Forest ecosystems of the region are rather low (less than 500eq/ha/yr). As a result of both the high SO2 emission rate and high sensitivity of ecosystems, the excessive input of acidity was calculated for more than 75% of the area considered (see also Chapter 15). 

Based on the mineralogy controlling weathering and soil development, sensitivity of ecosystems to acid deposition is assessed with the comprehensive consideration on the effect of temperature, soil texture, land use and precipitation. The results show... 

Critical load maps of acid deposition may be generated by calculation methods or by surrogate methods that attempt to assess the sensitivity of ecosystems to acidic depositions from readily available environmental information. 

As an interim measure, an assessment of the relative sensitivity of ecosystems to acidic depositions might prove useful so that tentative critical load values could be applied to the relative sensitMly classes and form the basis of target loads that could be used in abatement strategy models. One such attempt at mapping the relative sensitivity of eco stems to the Indirect effects of acidic depositions is now described. 

The sensitivity of a region to acidic deposition is related primarily to its capacity to reduce or chemically neutralize acidity. If there is an ability to quickly and effectively return conditions to nearly normal, the effects of the deposition will be minimized and the ecosystem is not considered to be sensitive. However, if there is little or no capacity to reduce the acidity, the ecosystem is highly sensitive and severe damage can occur if the acidic deposition is significant. 

Criteria 1) Relevance to human health endpoints. 2) Sensitivity to change in loadings. 3) Overall historical data quality. 4) Data collection infrastructure. 5) Feasibility of data collection and analysis. 6) Ability to adjust for confounding factors. 7) Understanding of linkages with rest of ecosystem. 8) Broad geographic distribution. 9) Well-known life history (for fauna). 10) Nonintrusive sampling. 

The accident at the Chernobyl, Ukraine, nuclear reactor on April 26, 1986, contaminated much of the northern hemisphere, especially Europe, by releasing large amounts of radiocesium-137 and other radionuclides into the environment. In the immediate vicinity of Chernobyl at least 30 people died, more than 115,000 others were evacuated, and the consumption of locally produced milk and other foods was banned because of radiocontamination. The most sensitive local ecosystems were the soil fauna and pine forest communities. Elsewhere, fallout from Chernobyl measurably contaminated freshwater, marine, and terrestrial ecosystems, including flesh and milk of domestic livestock. Reindeer (Rangifer tarandus) calves in Norway showed an increasing frequency of chromosomal aberrations that seemed to correlate with cesium-137 tissue concentrations tissue concentrations, in turn, were related to cesium-137 in lichens, an efficient absorber of airborne particles containing radiocesium and the main food source of reindeer during winter. A pattern similar to that of reindeer was documented in moose (Alces) in Scandinavia. 

The critical load concept is intended to achieve the maximum economic benefit from the reduction of pollutant emissions since it takes into account the estimates of differing sensitivity of various ecosystems to acid deposition. Thus, this concept is considered to be an alternative to the more expensive BAT (Best Available Technologies) concept (Posch et al., 1996). Critical load calculations and mapping allow the creation of ecological-economic optimization models with a corresponding assessment of minimum financial investments for achieving maximum environmental protection. 

Scope of the CLL approach. Critical loads and levels can be calculated for various specified sensitive elements of the environment (UNECE CLRTAP 2004, V-l). However, terrestrial and aquatic ecosystems are most frequently referred to as receptors in this effect-based approach. In addition, specific parts of ecosystems (e.g., populations of most valuable species) or ecosystem characteristics can be defined as receptors as well (UNECE CLRTAP, 2004). Such flexibility and established provisions for ecosystem assessment makes the CLL concept a promising solution for ecosystem risk assessment and a potential substitute for site-specific chemical RA following the bottom-up approach. 

Possible effects on soil hfe, plants (phytotoxicity) and on ground water are of concern in all types of ecosystems. Food quality criteria are, however, of relevance for arable land only, whereas possible secondary poisoning effects on domestic animals or terrestrial fauna are relevant in grassland and non-agricultural land. A final critical limit can be based on the most sensitive receptor. Even though effects vary for each metal, soil microbes and soil fauna are generally most sensitive. 

ERA in general is a process, as is EIA (Environmental Impact Assessment), and not the occasional report or document that is published at various steps. The framework for the orderly process, which has been developed for various environmentally sound projects can be applied also for acidification oriented projects and especially for an evaluation of ecosystem sensitivity to acid deposition and critical load calculations. Central management of the process is an essential feature. 

These combinations include the great variety of different ecosystems, the sensitivity of which to both acidification and eutrophication inputs by atmospheric pollutants differs greatly, determining the necessary reduction needs when CLs are exceeded by modern deposition levels. 

Table 4. Percentage of various endpoints contribution to total environmental risk assessment of ecosystem sensitivity to acid deposition in Northern Asia (Bashkin, 1998).

CNcrit, included in the calculation of critical nitrogen leaching, Ni(crit), values, the input of this endpoint parameter into the uncertainty of CL(N) is expressed in a lesser degree. Furthermore, the runoff processes are practically not significant for ecosystems of Luvic Phaeozems, Chernozems and Kashtanozems due to low P PE ratio. During the calculations of CL(N) for ecosystems of North East Asia, the values of critical immobilization and denitrification from N depositions as the endpoints both in relative and absolute meanings played a subordinate role that obviously reflects their minor contribution into uncertainty and sensitivity analysis of the computed output values of ecosystem sensitivity to acidic deposition. 

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