STRI Head of ecology and environment, Bob Taylor, considers the impact current trends in grassland management has on arachnids, and why we might be doing wrong, by doing right.
There has been so much attention given over the last few years to conserving our pollinators, such as the thinning of grasslands and encouraging gaps for wildflower establishment. Whilst this is wholly commendable, we are at risk of losing our more structurally diverse grasslands which are so important for smaller rodents, amphibians, reptiles and our spiders.
Arachnids are often overlooked simply because they are perhaps more difficult to identify than brightly coloured butterflies and our bumblebees, honey bees, hover flies etc.
A superb book has recently been produced; Britain’s Spiders: A Field Guide (Britain’s Wildlife) by Lawrence Bee, Geoff Oxford and Helen Smith which eloquently illustrates our unique arachnid fauna in all of the different niches they occupy.
The book splits the spiders by how many eyes they have. Some for example have six eyes, some have eight, and apparently looking directly into the eyes of a spider is vital if we are to accurately identify it. Good luck there then!
Golf course grasslands vary considerably, supporting an exceptional diversity of grasses and wild flowers, including many rare and specialist species. Other grasslands are tussocky and contain fewer flowers, but these are no less important.
These grasslands support better structural diversity and this is important. Structural diversity i.e. in height and form will support so many different species such as amphibians, rodents, day flying moths and spiders.
Management must be balanced, sensitive, and carefully considered. In the golf industry, we have become very successful at thinning grasslands through cutting, scarification and by using graminicides. Thinning the sward is better for play, and also botanically, as it can benefit wildflowers and pollinators.
However, by losing sward density, we are removing the structural form and diversity that will help to protect, cover and provide the many niches that the rest of our UK fauna require.
As I walk around golf courses, I constantly talk about the need to provide pollinator habitat, but I balance this by recommending that areas be managed less intensively to cater for the wealth of wildlife that within golf we can conserve.
This is where spiders come in; spider populations are heavily influenced by variation in vegetation structure and stability, and the amount of disturbance they receive. They are extremely sensitive to change! Management techniques for example will influence their niche.
Some spider species require unchanging “stable” conditions. They may require shade, stability of temperature and in vegetation structure. Those offline unmanaged grasslands support high structural complexity, and they are likely to have a well developed layer of fibre above ground, and thatch below ground.
The managed rough being more open, is also more prone to disturbance, and will support more ruderal or pioneering species. Management will influence which types of spider will exist – the pioneer or stress tolerator!
Spiders adopt differing foraging strategies, some for example can run or jump, whilst others wait with trap doors to lure and capture their pray. We’ve all seen the sheet webs, those sheets of silk with guide threads which direct and deflect pray into the web whilst the spider sits back and waits.
In disturbed ground, you will not find the more complex web builders. This habitat type will favour the more ephemeral webs prone to repeated and regular damage.
Cutting and management will also tend to favour those species likely to be found closer to the ground. Areas of unmanaged grassland, particularly supporting tussock forming grasses, or species such as fescue, will provide strong above ground fibre, and will support ground hunting spiders.
Interestingly these are more commonly associated with acid grasslands, with fewer species being noted within calcareous or heathland grasslands.
The point of all this is that varied management will maximise biodiversity, whereas working towards creating more open sward conditions which are certainly tidier, neater and beneficial for pollinators, will lead to a lack of overall diversity.
Therefore, in conclusion, try to aim to retain more open swards closer to the line of play, but do leave unmanaged grasslands further offline to optimise conservation interests.
Low intensity management will provide habitat for a range of spiders including many of our rarer species. Allowing structural variation through the grasslands will maximise opportunities for all our wildlife and importantly for spiders, particularly for those that prefer less disturbed and more complex habitats.
If interested in this subject, do checkout Britain’s Spiders: A Field Guide (Britain’s Wildlife) by Lawrence Bee, Geoff Oxford and Helen Smith, and also the online article Managing biodiversity in upland calcareous grassland landscapes: A case study of spiders and ground beetles (Lyonsetal.2018).