A study of lichens was undertaken for the first time ever. Lichens are destroyed especially by airborne sulphur dioxide, but also hydrogen fluoride, heavy metals, and other pollutants which tend to accumulate in them. Archival herbaries indicate that a deterioration of the atmosphere in Bohemia has been taking place roughly since the 1930s, but it has been only after 1950 that the process of disappearance of lichens assumed a conspicuously faster pace. The concentration of pollutants in the poorly ventilated meander of the Vltava valley presently permits the survival of just nine epiphytes out of the total number of 72 lichen species identified there. According to a British study analyzing the tolerance of different lichen species toward SO₂ alone, the local community of lichens is consistent with mean winter concentrations of sulphur dioxide ranging from 100 to 150 mg SO₂/m³.

Collected for the first time in 1997 the bryological data can only make use of a comparison with archival information dating back to the first half of the century to express a trend; it indicates the disappearance of a number of moss species particularly because of profound changes brought about by a rapid settlement in, and an ever-intensifying utilization of land. The current diversity of species situated mainly in the protected area of Havranka owing to its variety of stands is consistent with conditions existing there, and there is no rare or significant species that is especially sensitive to pollutants and be thus important as a bioindicator.

In the area under study the process of revitalization is clearly manifested on assemblages of molluscs which welcome not only a reduced volume of pollutants transported by air but also the development of a vegetation cover on slopes and of secondary groves with a dense and tall floor of herbs and rimming banks of streams. For many of their species the study has established a denser population and identified three previously unobserved new species.

A slight decline of the number of butterfly species and a considerable drop in their overall number compared to the previous inventories in 1987 and 1992 result from a long and hard winter, which have had similar consequences in the whole territory of Bohemia as well as elsewhere in Europe. The findings are regarded as indicative of a stabilized situation.

Some of forests have to put up with extraordinarily high numbers of visitors, which are also the reason of their more intensive maintenance (especially insofar as recreational elements and components are concerned) than that given to forests the purpose of which is timber production. In the Land-Use Plan, forests represent one of the most respected and protected categories of greenery.

Imission damage and timber production

	Units	1996	1997
Total forests	103 hectares	4.8	4.9
Healthy forests1)	103 hectares	-	-
Damaged forests2)	103 hectares	4.8	4.9
- including: damage level IV.a and IV.b	103 hectares	-	-
Damaged forests as % of total	%	100	100
Total timber production	103 m3 unbarked	14.1	13.8
- including: random	103 m3 unbarked	3.4	4.2
necessitated by insect pests	103 m3 unbarked	0.3	0.4

¹⁾ damage level - none
²⁾ damage level - 0/I az IV.b

Source: Ministry of Agriculture of the CR

 What is causing the problems with soil contamination? 

High concentrations of heavy metals or toxic organic substances were identified in the central part of the city, increased contamination was found around industrial facilities. The highest contamination levels are associated with illegal waste dumps. 

Some examples:

Troja - Bohnice

The area of Troja - Bohnice was selected for monitoring as one of the sites identified in the course of the geochemical mapping conducted by the Czech Geological Institute.
It has been confirmed that the area under observation is contaminated with cadmium and other hazardous elements. Although the concentrations “only” exceed Limit A as set forth in the Methodological Directive referred to above, they are substantially higher than elsewhere in Prague. Spots contaminated with nonpolar extractable substances (NES) and locally also with polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) have been identified as well. The source of the contamination may be sediments of the Vltava River and possibly also the chemical composition of the local rock environment. Additional anthropogeneous effects cannot be ruled out as well.
Save for PAH the agricultural soil quality does not suffer too much. An exception from the rule is represented by the contaminated garden next to House No. 268 in Troja.

Rohanský Island