Evaluation of habitats for nature conservation

To a greater extent than ever before, habitats and species are threatened.

Conservation will increasingly be required and involve: - designation of sites for various degrees of protection - implementation of management plans

How do you select a site for conservation?

Not all habitats can be conserved, and some habitats can be afforded greater priority for conservation than others.

This lecture introduces a number of important criteria that are used in assessing the conservation value of a site.

Anglesey is a large (72,000 ha) island off the north coast of Wales Lakes and reedbeds

support the greatest number of breeding wildfowl in Wales lime-rich fens are unique in Wales wildlife and plant communities rare or absent elsewhere in Wales

Wet pastures scattered across the farmland still provide food and breeding sites for wading birds.

Cors Erddreiniog

289-hectare SSSI, includes a 190-hectare National Nature Reserve and is the largest fen in Wales. Black bog rush Schoenus nigricans Blunt flowered rush, Juncus subnodulosus

Great fen sedge Cladium mariscus Fly orchid Ophrys insectifera Marsh gentian Gentiana pneumonanthe, Southern damselfly Coenagrion mercuriale at its most northerly location

Llyn Rhos-ddu

This shallow lake is dammed by the Newborough Warren sand dune system and is part of that National Nature Reserve. The lake supports a good range of aquatic

plants and animals including mare's-tail Hippuris vulgaris. Water level was accidentally lowered about 0.6 metres some years ago.

The AWS group has helped to install a sluice, being used to restore the water level.

Purple saxifrage Saxifraga oppositifolia

Snowdon lily Lloydia serotina

Rainbow beetle

Chough

Snowdonia

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

A word of caution…………...

These criteria are not definitive: they are not strictly independent, or all necessary for

consideration all of the time they are not entirely objective there are frequent exceptions

HOWEVER•they are intended to stimulate a comprehensive evaluation•they provide a structured evaluation process•they are widely and, with experience, reliably used

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Size

landscape suffers from severe fragmentation of natural habitat

A general ecological rule is that larger habitats contain proportionally more species than smaller habitats

species’ population sizes tend to be larger in larger habitats

But size isn’t everything!

Small areas may be of high quality/very rare habitat a small habitat may have a high proportion of the local,

national, or international population of a species

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Diversity

Physical, habitat, species and community diversity Usually, higher diversity is better

e.g. calcareous grasslands >50 species m-2

’improved’ grassland ~2 species m-2

However, diversity can be high, but of poor conservation value

Diversity is related to a number of different processes, and need to identify such processes that are important at a site

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Naturalness

More ‘natural’ implies: of greater conservation value absence of human interference (relative!) a natural habitat can change over time (succession, env.

conditions)

Need to consider: presence of introduced species how the habitat differs from other less disturbed habitats can the habitat be maintained/improved is another species dependent on it

Greenland whitefront goose favours grazing on improved grassland, the latter being of low intrinsic conservation value

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Rarity

Establish the wider distribution of a rare species/habitat local, regional, national, international?

Why is it rare? Limit of geographical distribution relict populations (e.g. Arctic alpine flora) specialised local requirements

Is it likely to continue to survive? (long-term viability)

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Fragility

‘the degree of sensitivity of habitats, communities, and species to environmental change, and so involves a combination of intrinsic and extrinsic features’ (Ratcliffe 1977)

Succession: natural dynamics of vegetation turnover Anthropogenic disturbances

how serious is the disturbance? (extent of damage) how likely is recovery?

Underlying causes of fragility? Viability? Within what timescale?

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Typicalness

Sites can be selected and valued because tjhey represent the best example of a particular habitat (which may not be threatened).

What is the typical landform/habitat/community for an area?

what are the typical species for a habitat/community?

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Recorded historyPosition in ecological unit

Habitat value may be enhanced if their history and management is known, for the management of one site, and understanding of others.

Availability and quality of scientific and land use records availability of accessible natural evidence

pollen record in peat bogs relevance of records to value of the features

Position in ecological unit most obvious example is offshore island reflects isolation, fragmentation, size of unit, buffer area,

quality of buffer area, land use around habitat

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration

Potential for improvement/restoration

Reflects isolation, fragmentation, size of unit, buffer area, quality of buffer area, land use around habitat

Habitats are usually imperfect Need to assess the potential for improvement can there be total recovery? Will partial recovery be adequate?

e.g. removal of weeds, Rhododendron removal of exotic predators

What features make a site of conservation value?

Size Diversity Naturalness Rarity Fragility Typicalness Recorded history Position in ecological unit Potential for improvement/restoration