Friday, 8 April 2011

Instability, transitions and trash

Get in there boy.

So, our 2-year project looking at the biodiversity of reedbeds has finally delivered its results...and we can at last squash an ongoing grumble about Bittern management and reedbeds. There has been a repeated accusation that management for Bitterns is bad for reedbed invertebrates, especially moths such as the Fenn’s Wainscot. Finally - there is NO evidence for this.

The headline results of the study are as follows, with the details here:

• The older, drier parts of the reedbed contained higher overall invertebrate diversity and many invertebrates with conservation status.

• Early successional reedbed is important for reedbed and wetland specialist invertebrates.

• The results show that having a variety of ditches and open water bodies is important for aquatic invertebrates and macrophytes.

• Reedbeds are dynamic ecosystems and temporal and spatial variation in habitats is key to maintaining high diversity of flora and fauna.  Management that maintains a range of successional stages will maximise the conservation value and biodiversity of reedbeds.

So, much as we had expected.

At a recent workshop with national invertebrate experts to discuss the project results, some key management themes to benefit inverts were outlined – in my words - 'instability, transitions and trash'. Now regular readers will recognise this as music to my ears.

Instability - we should accept that habitats change; managing a habitat to maintain a stable state of the natural succession, at whichever stage, will not work. Successions need to move on.
Transitions - gradations within and between habitats often support many specialist and scarce species; brackish to fresh, tall to short, wet to dry, new to old etc. etc..
Trash - 'catastrophic' management of part of the habitat to reset it to an early successional state will allow species to colonise at the appropriate stage.  As one of the entomologists stated ‘if it doesn’t spread, it’s dead’.

I have increasingly believed that the nature reserve system in the UK (all organisations) is creating a series of stable, increasingly dull sites. We need to inject some dynamics into the system, create early successional habitat. Heterogeneity is what we want, but homogeneity is what our systems tend to deliver. The more heterogeneity in the habitat, the more species a site will support. We have become scared of disturbance.

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