Map of Lough Erne Case Study and surrounding area. Source: Dr. Tim O'Higgins, University College of Cork

The overall goal of this study is to examine the implications of the regulation on invasive alien species for practical management in Lough Erne County Fermanagh, Northern Ireland in the context of existing environmental commitments under EU legislation. The hypothesis is that biodiversity and related ecosystem services targets can provide clear environmental management objectives for Lough Erne (see map).

Lough Erne sustains multiple competing primary activities each with different requirements from the system in terms of ecosystem services and biophysical abstraction. The Erne Loughs are heavily modified water bodies, and also contain a range of non-native origin with a very long history of introductions.  Balancing the needs of competing uses while also meeting the additional legislative burden of the IAS Directive requires consensus on ecosystem end-points as well as effective cross border cooperation. 

IAS are considered a major global threat to biodiversity resulting in extinctions (Sala, 2000; Clavero and Garcia-Berthou, 2005; Simberloff; 2013 Luque et al., 2014) and in major economic costs (Pimentel et al., 2000; 2005) and are now the subject of global efforts for control and eradication under the Aichi targets under the UN Convention on Biodiversity Strategic Plan for biodiversity (CBD 2014). However the science of AIS has received criticism on many fronts in particular the tendency for non-indigenous species to be considered ‘bad’  while indigenous biodiversity is inherently ‘good’, since ‘bad’ and ‘good’ are subjective value judgements and lack scientific objectivity (Brown and Sax, 2004). 

The most significant recent ecological development in the lake has been the arrival of the invasive zebra mussel (Dreisenna polymorpha) (Rossell et al., 1999, Maguire et al., 2006).  The mussel, first observed in 1996 has had profound effects on the trophic status of the lake, resulting in dramatic reductions in phytoplankton biomass (by about 10mg.chl m3 less than prior to invasion), and enhanced water clarity.  Since that time there has been an invasion (2006) and proliferation of the non-native Elodea nutallii this species spread rapidly in subsequent years, being able to colonise deeper areas due to the increased water clarity caused by the Zebra mussel (Kelly et al., 2015).  More recent non-native arrivals include the Blood red shrimp (Hemimysis anomala) (Gallagher et al. 2015) and the Freshwater jellyfish (Caspedacusta sowerbyi) (Lucy, 2013).

The IAS regulation places a number of new demands on European member states. Under the regulation a list of invasive alien species of union concern has been drawn up (Article 4) and a risk assessment must be produced for each species on the list (Article 5).  To date there have been two iterations of the listing process.  The listing process itself is an iterative process, candidate species are suggested by member states, these species undergo a transparent (subjective) qualitative review process based on scientific expert judgement.  Those species deemed to meet the relevant criteria including the existence of relevant risk assessments and a description of social environmental and economic “impacts” are passed on to a non-expert, non-public, governmental group IAS committee for listing.

There are many potential desirable management endpoints and many potential management options to reach these endpoints.  However identification of and selection of specific endpoints may involve trade-offs between different primary activities and different components of the ecosystem.  For the management of invasive species and specifically Elodea, physical removal of Elodea is not cost effective nor is artificial shading of the plants to reduce growth. One potential management option which could enable recreational activities is the raising of lake levels during the Summer time, to allow passage of boats over the Elodea (and possibly remove some stands of Eldoea by shading).  This option could require re-negotiation of the intergovernmental agreement on the Lough Erne levels. This option might also be contentious with farmers, as it could involve increased summer inundation of agricultural lands.  Since the Lough Erne area is prone to flooding, any discussion of raising water levels may prove contentious.

Two species, the European Eel and the Atlantic Salmon are the subject of intensive management efforts due to their (historic) commercial importance and dwindling numbers- Salmon for example are a species of least concern, but wild stocks in the Atlantic no longer support commercial fisheries.  The salmon in particular have been the subject of well documented and prolonged management efforts in terms of re-stocking, but for the Erne the rates of return of re-stocked fish have been very low.  This problem is common to many locations where hydroelectricity is located on salmon rivers (eg. O’Higgins, 2015).  In Lough Erne, a more detailed analysis of the economic value of the hydroelectricity (including the costs of current management efforts for salmon and eel) and the opportunity cost of a healthy salmon fishery in the Erne could favour prioritising recreational salmon fishing over the production of hydroelectricity.  In the Spey river (Scotland) for example the value of Salmon and Sea trout fisheries is estimated at GBP 11.6m annually or approximately (€13m) (Butler et al., 2008).

Area: Lough Erne, Co. Fermanagh NI is made of two parts, Upper Lough Erne and Lower Lough Erne both of which are widened channels of the River Erne, the second largest river in Ireland.  The former is a shallow, naturally eutrophic lake covering an area of 1,552 ha with a complex shoreline containing many small islands and peninsulas. Lower Lough Erne is a larger deeper lake with an area of 15,303 ha and a maximum depth ca. 60m, the two are joined by a section of the Erne river approximately 10km long.

Lead partner organisation: 

University College Cork, National University of Ireland is leading the research in the case study.

Cooperating Institution & Representative: 

Northern Ireland Department for Agriculture, Environment, and Rural Affairs (DAERA). The Water Unit of the Department of Agriculture, Environment and Rural Affairs (DAERA) is a cooperating partner for Case Study 4: Management and impact of Invasive Alien Species (IAS) in Lough Erne in Ireland. DAERA is a devolved Northern Irish government department in the Northern Ireland Executive. Until 2016 the department was called the Department of Agriculture and Rural Development. It has since been changed to also include the environment within its work remit. On this case study, DAERA is working closely with Waterways Ireland to ensure the sustainable management of Lough Erne particularly in light of invasive alien species and forecasted risks due to climate change and other activities within the catchment. DAERA and Case Study Four are represented on the SPBTT by Kerry Anderson.

Find out more about this case study:

Management and impact of Invasive Alien Species (IAS) in Lough Erne in Ireland