Deer and the Environment

Deer and the Environment. (1)

It has been said that :-

“The absence of certain species such as Deer and Grey Squirrel has a direct benefit for the woodland flora and fauna across the Island ”  and some ecologists fear that if wild deer were to be tolerated here they could “cause immense damage” to our woodlands with their “heavy browsing”.

But is this really true?

In the case of the Grey Squirrel and large concentrations of the invasive non-native Muntjac deer scientific evidence shows that this is indeed the case, but what of the other deer?

The Denny Pens study from the New Forest indicates what happens when you have too many deer. Two enclosures were studied, one control enclosure from which all large herbivores including deer were excluded and another which was artificially stocked with Fallow deer at an extremely high density of 100 / km2. After 22 years most understorey species were absent from the deer enclosure and tree regeneration had ceased.

So how does this relate to the Isle of Wight?

With around 50km2 of woodland this would require a deer population in excess of 5000 animals or by comparison more than double the deer population of the New Forest where  there are currently around 2000 naturally occurring deer spread over an area of around 230km2 of woodland.

So is there a level at which  a re-established Isle of Wight deer population would be beneficial?

Scientific research shows that low density deer populations increase biodiversity, typically at densities of 3/km2 – 7/km2 of woodland with a threshold of adverse impact on seedling regeneration occurring at 14 /km2.

In relation to the Isle of Wight this suggests that a beneficial deer capacity would be in the region of 150 – 350 animals and up to 700 deer before they would need to be reduced by a management cull.

Are there any other long term benefits for the island’s wildlife?

Large herbivore grazing and browsing such as by deer is necessary to prevent wood pasture and wood edge habitats scrubbing over.

The advance of this scrub would lead to the loss of flowering woodland plants. Once these flowering species are lost research shows they may be difficult to re-establish.

These are important feeding grounds for many of the woodland bat species found on the island and one of our rarest, the Greater Horseshoe, feeds on the coprophagous invertebrates associated with deer dung – perhaps this is why it is so scarce here.

So our woodlands – particularly wood pasture and edge habitats may actually be suffering from the relative absence of deer and not benefiting as some have claimed.

If you have seen some deer on the island please take part in the Isle of Wight Deer Survey  locations will be treated with strictest confidence. For periodic updates please visit Isle of Wight Deer Conservation or email  deerwight@gmail.com

Thank you for your interest and support

For more photos of deer on the Isle of Wight please see the Isle of Wight Deer Album

 

Wild Red deer Hind 30.4.2014(2)

A wild red deer hind resting in the understorey

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