Sunday, 19 June 2016

To graze or not to graze...

For years now 'conservation grazing' has become increasingly popular as a way of managing heathland as well as native grassland areas for wildlife. Both ponies and cattle are frequently used as well as other grazers such as goats and sheep , the aim being to replicate more traditional farming methods whilst controlling scrub encroachment onto more open areas. Each species has its own advantages and disadvantages and in general for the two most popular livestock these are:

● cattle do not graze selectively, which is good for creating diverse flower-rich swards; they can also push through scrub and eat taller, coarser vegetation and cut/dead vegetation
● they don’t graze too close to the ground and are therefore less likely to create bare patches than horses
● they leave areas of more tussocky vegetation, which are beneficial to invertebrates and small mammals
● not so good at coping with sites on steep slopes
● need more forage per animal and therefore might not be appropriate for very small sites

Horses and ponies
● horses can graze very close to the ground and so can leave bare patches of ground
● they are selective grazers and will leave some areas untouched, resulting in stands of taller vegetation
● they will eat tall grass, grass stems, and dead/cut vegetation
● they tend to defecate in specific areas (latrine areas) which causes a build-up of nutrient
● need more forage per animal and, as for cattle, might cause small sites to become overgrazed

When grazing is being considered as a form of management, risk assessments are often carried out - particularly in highly sensitive habitats. Strict recommendations are usually advised, including a max livestock density of .02 livestock units per ha (this varies depending on the livestock species being used) and indeed no grazing is recommended if the site in question is under 5 ha. How you impose these guidelines though is a bit of a mystery. The assumption is that animals will spread out evenly over a site but in reality they will often stick together or avoid areas where the feeding isn't as good thereby putting more pressure on other parts of the site. So is this form of land management actually helping preserve our vulnerable habitats? Relatively new research has shown that even grazing at the suggested livestock densities is having a detrimental effect on reptile populations and I believe wildlife generally. In parts of Europe studies have shown that reptiles have actually been extirpated from some sites since the introduction of grazing. The effects of mass trampling, over-eating in selected areas (forming an early successional habitat rather than the desired mid-successional) are taking their toll.

Evidence of these negative effects can be seen at a number of locations across our region too which, I have long believed, have contributed not only to a decline in reptile species but also in breeding birds such as the Tree Pipit, Meadow Pipit, Stonechat and Nightjar. Something which should be of concern to anyone interested in wildlife. Only last year I visited a know site for Smooth Snakes Coronella austriaca and Sand Lizards Lacerta agilis in Dorset to find cattle actually trampling the areas and refuges occupied by the reptiles.

These guys obviously haven't heard about
the 0.2 animals per hectar rule!
So should the practice of conservation grazing still be happening or is it case of over use of the wrong livestock species? Well, that's going to be a matter of conjecture but maybe the risks out-weigh the benefits? A study by Christopher J. Reading & Gabriela M. Jofré, published in The British Herpetological Society's 'The Herpetologist Journal' (Volume 26, Number 2 2016) shows conclusively that there were considerably higher numbers of reptiles found on surveys in areas of lowland heath that had not been grazed compared to areas which were grazed. The only exception to this finding was the Sand Lizard Lacerta agilis, which didn't appear to be effected by grazing (although they didn't benefit either). But it does make you question what we are trying to preserve, should we be conserving one species over all of the others?

Certainly there are sites on the Blackdown Hills close to me which have been heavily grazed by cattle in the name of conservation and the resulting habitat looks pretty poor to me. An opinion perhaps validated by the fact that this year there appears to be no evidence of breeding tree pipits or nightjars present for the first time in many years, not to mention a lack of reptile species!

But to balance the argument and end on a positive note I have seen what appears to be some excellent land management locally too. Trinity Hill near Axminster is an isolated patch of heathland and a local nature reserve, long know for it's specialised heathland species. Over the last couple of years the site has been well maintained and grazed by ponies.

There is a low density of ponies on site which are periodically moved across the heath and this appears to be making a very nice habitat for birds, insects and reptiles. There are no signs of over grazing here. So maybe it can be got right if those in charge know what they are really doing?

It will be interesting to see how Trinity develops as a habitat over the coming years and whether there will be an increase in breeding birds and reptile numbers there, I certainly hope so. I also hope that the recent research isn't applicable to this site, I guess only time will be the judge of that.

FOOTNOTE:  this story just came to light today. Talk about well timed!

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