Go back 250 years and beautiful heaths and remote moors covered much of Britain. Visited by characters from many well loved classics, such as The Hound of the Baskervilles, Pride and Prejudice and Tess of the d’Ubervilles, these atmospheric, but highly diverse habitats are an important part of British heritage and culture. On top of this, heaths are popular leisure areas for hikers, bikers and grouse shooters, who bring money into the local area. However, many heaths are being lost by increasing demands for new farmland. Professor Jane Memmott, leader of a team researching heathland restoration at the University of Bristol gave a seminar to the Animal and Plant sciences department in Sheffield discussing new approaches to combating damage to heathlands.
Memmott argued that an ecosystem such as a heathland is like a machine, with many working parts that do different jobs. Animal and plant species, the birds, the bees and the buttercups, are the cogs and gears of the machine, each with its own role to play. Exhaust pipes remove fumes while axles let car wheels turn. On a heath, bees pollinate flowers, buttercups turn sunlight into food and nightjars eat insects which would otherwise swarm everywhere.
Attempts to restore animals and plants that have dissappeared from heaths have begun, despite the problems caused by continuing demands for farmland. The restoration of habitats is a difficult prospect but Memmott’s team are leading the way in developing new tools for applied ecologists. The most important of these tools is the food web. Food webs have many invaluable applications, such as being able to predict the effects of removing a pest species.
The challenges facing heathland restoration are threefold. Firstly, the ‘fuzzy target problem’ is that we have limited knowledge of which animals and plants lived on a heath before it was turned into farmland. If we do not know what it is we are restoring, how can we know if we are succeeding? Secondly, the ‘moving target problem’ is that heaths are constantly changing, and so even if we knew what a heath was like before farming, how can we know what it would be like now had it not been damaged? Finally, the ‘experimental design problem’ is that every area of heath is different, even if they are quite nearby. In more extreme cases such as tropical rainforests, each tree has its own set of insect species! How can we do proper scientific experiments, and thus backup any claims of successful restoration, in a world where each area is unique? These are some of the problems being tackled by Memmott’s team, especially in their restoration research in the Dorset heathlands. A large focus of this work is the utility of food webs for practical ecologist.
What to restore?
One way of dealing with the problems caused by the the ‘fuzzy target problem’ may be to define our targets (what we hope to be left with after restoration) in a different, more flexible way. Instead of focusing on the individual animal and plant species, argues Memmott, we should aim to restore the roles (such as pollination or herbivory) that they played in the heathland ‘machine’. This avoids the fuzzy target problem by creating a new target that is common to many areas of heathland. If a car engine needs to be replaced, it doesn’t matter if the new engine is exactly the same, as long as it turns the wheels. Memmott claimed that getting the car running is the most important task.
Using food webs and focusing on the roles played by plants and animals also tackles the ‘moving target problem’. The plants and animals that live on a heathland are always changing as a plant or animal might become locally extinct and will be replaced by a new, invading species. However, a herbivore will be replaced by a new herbivore and a parasite replaced by another parasite and the heath will remain healthy. Beause of this, all we can aim for is the restoration of the various roles in the machine, as we can never really know whether or not the individual species would have dissappeared from the heath even if it had not been turned into farmland. If we were to restore the Titanic, you wouldn’t hope to have exactly the same chairs as the original. As long as the chairs looked about the same, the restoration would count as a success.
This more abstract approach is the beginning of a new way of looking at restoration. However, being new it is lacking many of the tools needed for it to work efficiently. Memmott claims that food webs, including plant-pollinator webs are one major tool that are not yet exploited fully, especially in terms of studying interactions other than predation and herbivory. Memmott and her team has “made the first ever plant-pollinator network.” This network can be seen below and shows which insects (top) pollinate which plants (bottom). If an insect often pollinates a particular plant, they are linked with a thicker line. These food webs allows ecologists to visualise and record who’s doing what on a heath, define targets for restoration, and finally to predict the effects of adding or removing a species. “Although removing an alien species could help rare species in the area, it may also make them even rarer by decreasing pollinator numbers.” explains Memmott.
The restoration of habitats such as heathlands is a daunting task and the development of practical tools to aid field ecologists is vital. This work is in its fledgling stages, but is being advanced by the hard work of scientists such as Memmott and her team. All this however is only one part of the challenge of restoration. A larger and harder problem still lies with the difficulties presented by development, human population increase and an increasing demand for farmland. Field ecologists can have a box full of useful tools and all the good will in the world, but it is all in vain if their work is stopped by farmers and other people who want to keep changing heaths into farmland.