Hungry deer should not be barred from grazing in protected native forests, botanists have urged.
A decades-long study of national parks in Ireland has found that grazing deer in oak woodlands is actually good for diversity and helps prevent some plants from taking over the valuable ecosystem.
Researchers found that if red and sika deer and the red-sika hybrid are fenced off, or shot in annual culls as a way of protecting the forest, it becomes significantly less diverse.
But botanists from the School of Natural Sciences in Trinity College Dublin warned that attempts to reintroduce deer should be in moderation, as uncontrolled grazing will also have a damaging effect on the woods.
A network of seven experimental deer “exclosures” were surveyed periodically in three national parks in Ireland over 41 years to try to explain how woods grow and change over time.
The sites inside protected oak woodlands in the Wicklow Mountains, Killarney, Co Kerry, and Glenveagh, Donegal, revealed the surprising results that stopping hungry deer from munching on plants actually decreases floral biodiversity.
Researcher Dr Miles Newman said deer grazing at the correct level is highly important for the conservation of native oak woodlands.
“Our results certainly have implications for the management of these woodlands as future policy should focus on managing deer — rather than simply excluding them — as part of the overall biodiversity objective,” he said.
“We are now working on the next step to identify what the optimal level of deer grazing may be.”
The results of the study are published in the journal Forest Ecology and Management.
They show that when deer are blocked from semi-natural oak woodlands, the composition and abundance of forest-floor plants is greatly changed.
Meanwhile, Noel Grimes, of the Kerry Deer Society, had dismissed claims made at Kerry County Council that deer are carriers of TB which affects cattle.
He agreed with the Department of Agriculture that deer are not responsible for the spread of TB among cattle and told people making claims to calm down, to stop looking for excuses and get a few facts correct.
“Could it be that cattle are passing TB on to deer?’’ he asked.
Mr Grimes also agreed that something positive needed to be done about the deer situation — and called for a national count of deer.
‘’Some areas are over-run by deer, while there are very few deer in more areas.
“If we had the figures, something could then be done about the problem,’’ he said.
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