4.1b Species diversity

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76 FOREST REPORT 2005

4.1b Species diversity

Forests are traditional habitats or ecological retreats for almost half of Switzerland’ s plants and animals.

Forest landscapes with open canopy often provide a last refuge for many threatened animals and plants living in open habitats.

Forests can apparently mitigate the effects of climatic extremes like the heatwave in 2003

better than most other ecosystems, to the benefit of forest dwellers.

Development of species diversity

TwoSwiss projectsarecurrently devoted todevelopingspeciesdi- versity indifferent habitats.“Bio- diversity MonitoringSwitzerland”

(BDM) documents the develop-

ment of selected plant and ani- mal groups in different habitats and at different altitudes.The so- called“RapidBiodiversity Assess- ment”records the species diversity of insects and spiders at 20 forest sites.

There are not yet any long- termobservationsavailable from BDM, but it is already possible to say something about the dis- tribution of flowering plants, ferns,mosses and snails. Vascu- lar plants,for example,which include floweringplantsandferns, aremost species rich in subalpine regions and are more abundant in meadows and pastures at all altitudes than in forests.The op- posite,however,applies to snails:

most speciesliveat lowaltitudes, preferably in forests.

The number of insect and spider speciesat 42sites inboth forest andopencountry inSwit- zerland has been recorded each year since 2000 as part of the

“Rapid Biodiversity Assessment”

project. These surveys have shown that more species live on agricultural land than in forests, and this tendency is increasing.

This trend is presumably a pos- itive outcome of compensatory payments in agriculture, which, for instance,support establishing field edges that are rich in species.Incontrast,forestscan offer amore stable habitat.Thus,during the heatwave in2003species numbers in fields,cropland and meadows fell,but rose in forests.

This indicates that forestswillbe- come evenmore important as ec- ologicalsanctuariesduring periods ofclimatewarming.

Studies ofbirds breeding in Switzerlandhavealso shown that forestsarecomparably stable ec- FURTHERINFORMATION

Swiss Federal Research Institute WSL 8903 Birmensdorf

Research Dept. LANDSCAPE Section Biodiversity (0) 44/ 739 23 76

Swiss Ornithological Institute 6204 Sempach

(0) 41/ 462 97 00

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77 4BIOLOGICAL DIVERSITY

osystems.Nearly 40% of thebirds that regularly breed in Switzer- land are endangered. Of those that breed in forests, however, only 12% are threatened. Many of the58species ofbird that live and breed in Swiss forests have evenmanaged to spread,e.g. the bluetit,blackwoodpecker,marsh tit and blackcap. Nevertheless, several species that have spe- cialenvironmentalrequirements have disappeared in many plac- es. These include the nightjar, grey-headed woodpecker,caper- caillie, nightingale, willow war- bler, golden oriole, woodcock, middle-spotted woodpecker and hazel grouse. The reasons for this development are primarily the decline of previously prac- tised forms of agriculture, such aswoodedpastures,coppice forest,and coppicewith standards, as well as the increasing stand density andlackoflight inmany forests.

Forest species

Animals and plants are consid- ered tobe forest species if they spend all or part of their lives in forestsand could not survive without forests.Many specieslive in the transition zone between forestsandopencountry:on forest edges,in shrubforestsandin woodedpastures.

But how many plants and animals live in the forest or on its borders? Currently, some re- searchers are trying to answer thisquestion.They havecatego- risednearly 6500species fromele- ven important animaland plant groupsas either“forest”or“non-

forest”.It seems that at least 36%

of theanimalspeciesand38% of the plantsdepend on the forest as a habitat either wholly or in part.Thedifferencesbetween the different groups of organismsare striking:only 16% of theground beetlesare forest species,where- as 89% of the longhorn beetles are. The species studied make up only 13% of the over 50000 plants, animals and fungi that havebeen found todate inSwit- zerland. Nevertheless, the first preliminary results of the study demonstrate howimportant forests are for Switzerland’s biodiversity.

4.1b.1

Species diversity in Swiss forests

Comparisonof themean species diversity within10m²in theforest with the diversity in meadows and pastureland.Data at the95%confidence levelfrom Biodiversity MonitoringSwitzerland(2001-2003).

Vascular plants Mosses Molluscs Forest Meadow/

pastureland

Forest Meadow/

pastureland

Forest Meadow/

pastureland Switzer-

land

20 ± 2 37±3 14 ± 1 7± 1 8 ± 1 6± 1

Low altitudes

18±4 29±6 8± 2 3±1 10 ±4 9± 3

Montane 18± 2 32 ± 3 13 ±1 5±1 10 ± 2 6±1 Subalpine 23 ±4 48±5 16± 2 11± 2 5±1 4±1

4.1b.2

Proportion of forest species in each organism group

Number and proportionof species in Switzerland that livewholly or partially on theforest and dependonit.

100 80 60 40 20 0

[%] ■Non-forest

species

■Forest species

2122 626 165 255 40 137 8 13 22 418 165 182

471 467 621 345 44 58 6 6 182 80 37 95

Forests will become even more important as ecological sanctuaries during periods of climate warming.

Vascular plants

Reptiles Breeding

birds Mamm

als Largefungi Lichens Mosses

Molluscs Butterflies Groundbeetles Longho

rn beetles Amphi

bians