Biological recording and the drivers of change in freshwater

Biological recording and the drivers of change in freshwater

Roy Anderson

Objectives

Red list aquatic invertebrates to:

Improve knowledge of

Faunal composition

Habitat association

Change over time

Strategy

Mapping schemes Require some public participation

Guided by a body of dedicated people driving and co-ordinating/validating

Ideally with regular updates via websites

Eventually, publication of atlases

Outcome

Mapping schemes Red Lists The Red Listing process should:

Obtain and encode all historical data Compare with modern results Be subject to periodic update as new data becomes

available Classify fauna according to IUCN guidelines and register

level of threat Draw in available habitat, climate and water quality data to

compare with faunal distribution and relate to perceived changes in that distribution

Adephaga

Aquatic and semi-aquatic Adephaga Red List published in 2009 244 taxa recorded belonging to 16 families, both fully aquatic

and marginal; 73 red-listed i.e. 30%

Measuring change

Data from early twentieth century compared with recent data to determine change in status

Regional extinction risk

A – past, present or future population decline

B – restricted range, fragmentation, continuing decline

C – small population size and continuing decline

D – very small populations in decline

Evaluation Only a small minority of the declining species were considered to

be in a general population decline i.e. a decline across the country by comparing distribution pre and post 1980 (category A2)

The vast majority of highly threatened species were considered a priori to have fragmented ranges or specific requirements (stenotopy) which was related to decline (category B2)

A large number placed in a lower threat category (VU) were considered at risk because of the small population size or limited number of available sites (category D2)

A similar number were also classed as near threatened (category A3) because of more general decline, but related to reliance on a specific habitat

Many species associated with fen habitats showed little real evidence of decline but were classified as at high risk because of findings outside Ireland

The habitat with most at risk species was fen (next slide) but few fen species actually show a decline in Ireland!

Habitat associated decline

Siltation - river gravels/lakeshores

Also here: Enicocerus exsculptus, Bidessus minutissimus, Hygrotus novemlineatus (? diffuse pollution)

Drainage - brackish habitats - lagoons

Also here: Ochthebius marinus, Haliplus apicalis, Helophorus fulgidicollis, Enochrus halophilus

Warming - montane sites and species

Also here: Dytiscus lapponicus. Stictotarsus multilineatus, Agabus arcticus

Mollusca

Measuring change

Red List published in 2009

150 total native spp of which 53 are red-listed: i.e. 35%

79 aquatic of which 31 are red-listed i.e. 39%

Regional extinction risk

A – past, present or future population declineB – restricted range, fragmentation, continuing declineC – small population size and continuing declineD – very small populations in decline

Evaluation

Very different from Adephaga

Risk seems to have its greatest concentration in category A suggesting general decline rather than association with rare habitats (stenotopy) or having a previously fragmented range

This suggests that an important environmental variable has changed recently and is affecting many species

Examples

Eutrophication/diffuse pollutionMyxas glutinosa

Glutinous snail

IUCN Endangered

A2c

A declining species across its entire west palaearctic range.

Ireland is now its headquarters with up to 50% of global population.

Needs gently flowing, low-P calcareous waters.

Also here: Omphiscola glabra, Anisus vortex, Radix auricularia, Margaritifera margaritifera, Pisidium lilljeborgii, P. pulchellum, P. moitessierianum

Pre-1980 Post-1980

Drainage and Eutrophication

Omphiscola glabra

Mud snail

[IUCN Extinct ] – Critically endangered

A declining species across most of Europe.

Confined to the south-east, and recently re-discovered at a site in Co Waterford.

Requires low-P poor fen or undrained low-nutrient riverine marshes

Pre-1980 Post-1980

Drainage – freshwater marshes, floodplains

Aplexa hypnorum

Moss bladder snail

IUCN Vulnerable

A2c

Widespread Palaearctic species living in temporary habitats, especially on winter-flooding lakeshores and riverbanks.

Declining thro’ habitat destruction

Also here: Quickella arenaria, Succinella oblonga, Vertigo antivertigo, V. moulinsiana, Musculium lacustre, Sphaerium nucleus

Pre-1980 Post-1980

Drainage - brackish habitats - lagoons

Hydrobia acuta neglecta

Hydrobiid snail

IUCN Endangered

B2a,b(iii,iv)

A north European endemic.

Confined to coastal lagoons of high salinity.

Four known sites, two of which have recently been destroyed by drainage/changes in management.

Also here: Ventrosia ventrosa, Truncatella subcylindrica, Mercuria cf. similis

Pre-1980 Post-1980

Warming - montane sites and species

Pisidium conventus

Arctic-alpine pea mussel

IUCN Critically Endangered

B2ab(i,ii,iii,iv)

Boreal relict, probably in steep decline. Only one recent site.

Conclusions

Drivers of change Both Coleoptera and molluscs suffer from diffuse pollution via its effects on algal growth, de-oxygenation etc.

This reaction appears more restrained in Coleoptera which are threatened more by range fragmentation and destruction of specific fen and peatland types

Molluscs are possibly unable to escape the effects of diffuse pollution because they and are less mobile and have a more permeable integument

May be good indicators of pollution, both point source & diffuse

Beetles may be more useful in assessing the decline of specific habitats

Brackish habitats home to both groups continue to decline and pose a threat to many stenotopic species

Warming affects only one mollusc but a number of beetles