Disturbance Study
Disturbance Study Completed!
Commissioned by the Exe Estuary Partnership, the Disturbance Study was carried out to determine the extent and nature of disturbance of wintering waterfowl from human activities on the Exe Estuary. Durwyn Liley of Footprint Ecology carried out the study, which is now complete and available to the public.
Click here to access the Disturbance Study Report and Map Annex
What is Disturbance and Why Does it Matter?
During the winter months, around 25,000 migrating birds rely on the Exe Estuary as a place to rest and feed to replace the calories lost on their long migratory journey from Siberian Russia. The importance of this site for this purpose has resulted in the estuary being internationally recognised as a Special Protection Area (SPA), which means that particular duties are in place to adequately protect these birds, including the management of disturbance.
Disturbance is when human activities result in a change in behaviour of birds, usually unintentionally. Since birds view people as predators, this can result in birds avoiding areas entirely, which can reduce their feeding, leaving them with less energy for long distance flights during migration. Although a single disruption of these birds may seem harmless, the combined effect of repeated disturbance can be catastrophic, and has been known to result in the death of entire flocks of birds within just a few hours.
The Exe is a very busy place, so a decision was made by the Exe Estuary Partnership to commission a Disturbance Study to determine the effects of the wide variety of activities in the area. A novel and fresh approach was taken to combine existing bird distribution and behavioural responses with direct observation on birds and data from users themselves, including GPS track data for a range of different water sport activities to explore how & where they take place. This data was used to estimate the area of intertidal habitat lost to the birds from different activities.
Map: An example of GPS Routes for Kite Surfing. 36 different
routes shown, collected on 11 different dates during 2009-
2011 showing two clear areas used by kite surfers.
Summary of Results from Footprint Ecology
A wide range of different activities occur around the Exe and overlap in time and space. Water based activities involve a wide range of craft, and include both commercial and recreational use. A range of shore-based activities also take place and people were regularly recorded on the intertidal, below the mean high water mark. Taking an overview of access, the estuary is clearly very busy and it is only a small proportion of the perimeter of the estuary where access is limited or difficult. The highest levels of access occur around the lower stretches of the estuary, at Exmouth and also at the very top of the estuary, around Topsham.
After controlling for distance, tide and location, birds were more likely to take flight when the activity took place on the intertidal or on the water compared to the shore. Bait digging on the intertidal, dog walking with dogs off leads on the intertidal, walking on the shore and intertidal and kitesurfing are the activities which account for the majority of major flight events. It is dog walkers with their dogs off leads on the intertidal that caused the highest percentage of major flights from all the observed potential disturbance events.
Table: Responses of birds (grouped across all sites and all species) according to activity. Activities are listed in order of sample size (the sample size being the number of species specific observations, given in brackets).
We use the actual route data from visitor work (GPS tracks and face to face interviews) and the analysis of flight response to calculate comparative ‘areas’ of intertidal habitat lost as a result of different activity types. These calculations suggest that, at intermediate tide stages, the average area lost to a windsurfer or kitesurfer would be around 8ha, while a dog walker on the mudflats at the duck pond results in an area lost of around 3ha (note that this figure is likely to underestimate the impact of dogs as we only have route data for the owners rather than the pet). By contrast the disturbance caused by someone walking along the shore path at Goat Walk at low tide equates to an equivalent impact of the loss of 0.1ha of intertidal habitat to the birds.
What Next?
It has been shown that watersport users and flocks of birds can co-exist happily on the water, as long as certain measures are adhered to. This groundbreaking study will not only improve our understanding of the impact of recreation on the estuary, but it will also help us to work out how this can be effectively managed alongside nature conservation, involving local user groups where possible. Some management practices are already in place, such as voluntary codes of conduct, exclusion zones and keeping dogs on leads in certain areas. Most water users have proved to be very considerate to these measures, and as a result, they prove to be effective at minimising environmental impact and have even prevented complete bans of certain watersport activities. Please be aware of any restrictions which are in place when you visit the Exe.
We also need to look into the future. For example, several new housing developments have been approved in East Devon, Exeter and Teignbridge. The Management Partnership will need to take increased visitor numbers into account when considering the impact that recreation will have on the delicate habitat which is the Exe Estuary in the years and decades ahead.
But it’s not just on the Exe that this work will have a big impact. The study could influence how other globally important habitats across Britain are managed. The Exe Estuary Partnership now has a much clearer understanding of which recreational activities have the greatest impact on wintering bird populations, which we can share with other Coastal Partnerships across the UK. The study has even been praised at a European conference in France, following a presentation given by the Exe Estuary Partnership at the "Nature and Sports Euro'Meet", attended by 19 countries. Feedback following the presentation indicated that other European countries were keen to adopt this new and innovative approach on their sites.
Durwyn Liley, Footprint Ecology
Durwyn Liley at Footprint Ecology is a world-leader in carrying out this kind of research. Human disturbance and access have been key research interests throughout his career - which started with his doctoral research, exploring the consequences of shoreline access for Ringed Plovers in Norfolk. Durwyn has also worked as a warden with the RSPB, as a project manager for the RSPB, as a research ecologist for Butterfly Conservation, as an ecologist for Birdlife International and as a conservation officer for English Nature. Birds have always been an over-riding passion since childhood and Durwyn has worked on a wide variety of species and bird conservation projects – including work in Canada, Pakistan, Indonesia, Paraguay, Israel, Bolivia, Fiji and New Zealand. Durwyn is a keen all round naturalist with a wider interest within the UK that encompasses cetaceans, hoverflies, dragonflies and plants.
He co-founded Footprint Ecology in 2005 as a way of using his skills and experience to contribute directly to nature conservation while integrating his environmental principles. Footprint Ecology now employs eight staff and works across southern England, exploring ways to integrate people and nature conservation. Footprint Ecology’s recent work includes advice to various local authorities relating to housing distribution in relation to protected sites, research into heathland birds and access, work on night-time foraging of waders in Poole Harbour (in relation to access levels), work in the Solent on access and disturbance, access monitoring and visitor studies at a range of sites and various projects to reinstate grazing on commons.
Contact details:
Durwyn Liley, Footprint Ecology
Email: info@footprint-ecology.co.uk
Web: www.footprint-ecology.co.uk
Funders
This collaborative study has been funded by the Environment Agency as part of ‘Enjoying Water’: A Strategy for water based recreation in the South West’ - which can be viewed online at: www.environment-agency.gov.uk/homeandleisure/recreation/101708.aspx Additional funding has also been provided by Natural England and Interreg IV A 2 Seas through BALANCE. Key input was received from Teignbridge & East Devon District Councils, RSPB and Devon County Council.
Stephanie Clark, Exe Estuary Officer
Tel: 01392 382236
Email: exeestua@devon.gov.uk