The Impact of the REPS on Biodiversity: Are Measures Benefiting Plants and Insects on Farmland?
Dr. Jane Feehan, European Environment Agency, Former Research Scientist, Teagasc/Trinity College
Introduction
Little ecological evaluation of the Rural Environment Protection Scheme (REPS) has been done to date, and in particular, evaluation of the scheme's impact on farmland biodiversity has been neglected. As part of a Teagasc Walsh Fellowship project, the effects that certain REPS measures may be having on plant and insect species diversity were examined.
When the scheme was first devised one of its stated objectives was `to protect wildlife habitats and endangered species of flora and fauna', but throughout the scheme's specifications the overwhelming emphasis is on water pollution reduction and extensification, and the word `bio-diversity' appears only once in the REPS handbook, despite several revisions. One of the objectives of this research is to make specific, practical recommendations for ways in which the REPS could be improved with regard to the protection and maintenance of agri-biodiversity. Several such recommendations are presented and discussed in this paper.
REPS measures and biodiversity
Amongst the compulsory REPS measures, four were selected as having particular relevance to the biodiversity of wild flora and fauna on farmland. These measures are as follows (Department of Agriculture, Food and Rural Development, 2000):
Measure 3 - Protect and maintain watercourses and wells
Measure 5 - Maintain farm and field boundaries
Measure 6 - Cease using herbicides, pesticides and fertilisers in and around hedgerows, ponds and streams
Measure 9 - Tillage crop production
Measure 4, under which habitats are retained, was not examined because it is not currently applied on the majority of REPS farms.
In order to assess these measures, fieldwork was conducted on 60 grassland and tillage farms in Counties Laois, Offaly and Wexford during 1999 and 2000. Equal numbers of REPS and non-REPS farms were included in the study. Selected REPS farms had been in the scheme for at least four years. Hedges, field margins and watercourse margins were surveyed using quadrat methods and pitfall trapping.
In the light of the data collected, the success of each of these measures in maintaining or enhancing flora and insect fauna species diversity is discussed, and recommendations are summarised.
Measure 3 - `Protect and maintain watercourses and wells'
The principal objective of this measure is to reduce water pollution, but it also states that streams and watercourses should be fenced off to protect the flora and allow it to develop.
Impact of Measure 3
The average number of plant species per farm in 11 fenced REPS watercourse margins and 11 unfenced non-REPS watercourse margins were compared (Fig. 1). Higher numbers were found on non-REPS unfenced margins, but the difference is not significant.
Figure 2 shows the relationship between fence distance and plant species diversity on surveyed watercourse margins. There is no significant correlation between fence distance and plant species diversity. Wider fences don't have higher numbers of plant species. These findings correspond with research elsewhere which concluded that concludes that grazing and cutting are important factors in the maintenance of plant and invertebrate diversity, both in field margins and alongside watercourses (Bakker and Berendse, 1999; Schmid and Wiedemeier, 1999).
Measure 3: Recommendations
It is concluded that this measure should not require the compulsory fencing off of every watercourse that is wet for nine months of the year. Some of the smaller drains and streams should be left unfenced to allow the streamside vegetation to be grazed, keeping the watercourse free-flowing and maintaining the flora that persists alongside it.
Measure 5 - `Maintain farm and field boundaries'
This measure specifies guidelines for hedgerow maintenance and protection. It has been expanded and altered since the early days of the scheme.
Impact of Measure 5
Amongst the hedges that were surveyed on grassland, it was found that fewer beetle species were recorded from alongside gappy hedges. It appears that gappy hedges are less effective in providing shelter and protection to beetles. This is a tentative endorsement of the gapping-up that is being done on many REPS hedges.
Gappiness emerged as being more important in relation to the carabid community than to the field margin flora. Hedge age and height were important in explaining variation in the field margin plant data, but there was not a simple relationship between these variables and species diversity.
Measure 6 - `Cease using herbicides, pesticides and fertilisers in and around hedgerows, ponds and streams'
A spray limit of 1.5m around hedgerows and streams is specified by this measure. The main challenge to assessing the impact of this measure is the fact that 1.5m is very little - it is similar to what most farmers would be doing anyway.
Impact of Measure 6
Only 27% of the grassland REPS farmers surveyed said that the REPS incurred a reduction in field margin inputs on their farm. Many were unaware of the need to do so at all, and some of those who were aware of the measure appeared to assume that it applied to herbicides and pesticides and not to fertilisers. On tillage farms, most REPS farmers said that they were reducing inputs in the margins, and indeed P levels were significantly lower in the REPS inner field margin area (p=0.013).
Focusing on the diversity of this 1.5m field margin area on surveyed farms, the following results were obtained.
Non-REPS grassland field margins had significantly more (14.2±3.5) plant species per farm than REPS (12.5±3.3) grassland margins (1-tailed t-test, p=0.009) (Fig. 3). When the total of all REPS and non-REPS species were pooled together (ie not just farm averages), slightly more plant species were recorded from the REPS farms than from the non-REPS farms (Fig. 4).
- On tillage field margins, average plant species richness did not significantly differ between REPS (11.1±3) and non-REPS (10.8±3.8) farms (2-sample t-test p=0.66). A total of 81 species were recorded in all the surveyed REPS tillage field margins together, 72 on non-REPS margins.
- There were no significant differences between the ground beetle species richness of REPS and non-REPS margins, either on grassland or tillage farms.
It is concluded that input reductions are either not being achieved in the surveyed grassland field and watercourse margins, or if they are, no significant impact on floral diversity is observed. In tillage field margins, it would appear that input reductions are being achieved, and species richness in REPS margins is indeed higher than on REPS margins, but not significantly so.
Measure 6: Recommendations
It is strongly recommended that the 1.5m limit be extended to at least 3m. A 1.5m limit does not allow for the spray drift that inevitably occurs on occasion. The same applies during fertiliser application. It has been demonstrated elsewhere that a 3m buffer strip reduces spray drift into ditches and hedges, lessening the disturbance to field margin flora from farming operations (De Snoo and De Wit, 1998). With some spraying apparatus the sprayer can be turned in or switched off on one side so that drift can be minimised when the outer perimeter is being sprayed. It is recommended that this be done wherever possible.
Measure 9 - `Tillage crop production'
One of the requirements of Measure 4 is that an uncultivated strip of at least 1.5m be retained at the margin of the field.
Impact of Measure 9
On surveyed tillage farms, REPS fields (average 181cm) had significantly wider margins than non-REPS fields (average 145cm) (p<0.001). The surveyed REPS field margins were also significantly lower in P (5.94 units±3.98) than those of the non-REPS farms surveyed (9.19 units±6.53) (p=0.025).
Wider uncultivated field margins did not significantly benefit either the plant diversity or the beetle diversity data on surveyed farms.
Although the wider margins did not appear to enhance beetle diversity, slightly higher abundances of beetles (particularly Harpalus rufipes) and shrews (Sorex minutus) were recorded. This is an encouraging sign that the wider tillage margins may provide a very real benefit, because many of these beetles are predators of crop pests. For example, Bembidion lampros is an important predator of root fly eggs, Harpalus species consume large numbers of weed seeds, and several carabid species reduce aphid populations in the crop (Thiele, 1977; Kromp, 1999).
Measure 9: Recommendations
A recommended improvement to this measure is the widening of the uncultivated strip to 3m, and the introduction of occasional 6m-wide reseeded strips in selected locations. Research in the UK has found that widening margins to several metres does benefit flora (Moonen and Marshall, 2001). It is thought that the widening of tillage margins to 3m or more would indeed see an increase in plant species numbers. There is also a need to introduce cropping and removal of vegetation in tillage field margins, e.g. by grazing them after harvesting, in order to bleed nutrients and accelerate the development of less weedy, perennial flora.
Summary of results and recommendations
- Non-REPS grassland field margins were found to be significantly richer in plant species richness than surveyed REPS farms.
- Effective communication of the rationale behind eliminating inputs in the field margins, and practical advice on how best to achieve this, are needed. It is recommended that on all grassland REPS farms, a minimum area of 3m (rather than 1.5m) from the hedgerow should be kept input-free, and grazed/topped as usual. A key problem that needs to be tackled is the spreading practices of contractors, particularly the spreading of slurry in field margins.
- REPS tillage field margins were found to be significantly wider and significantly lower in P than non-REPS field margins. However, this had no apparent effects on plant or beetle species richness. There were higher numbers of beetles and shrews though, which is an encouraging sign that the wider margins may be having some beneficial impact.
- On tillage land, the current 1.5m field margins width is simply too narrow for the establishment of a less invasive perennial vegetation. The uncultivated margin area should be increased to at least 3m, with a much wider input-free buffer zone to allow for drift. Restoration options such as reseeding, and occasional wider `beetle banks' for pest-eating beetles.
- Fenced watercourse margins are not higher in plant diversity. In fact, higher numbers of species were recorded in unfenced margins.
- It is not necessary for all watercourses on REPS farms to be fenced off. The results of this study have shown that universal fencing of watercourses would be likely to incur a loss of plant species, particularly those low-growing species which depend on the continuation of grazing management to retain their place in the community.
Essential monitoring still not being done
There is a statutory requirement to monitor all EU agri-environment schemes, including the REPS. Although the REPS has been subject to several once-off, small-scale surveys examining aspects of its ecological impact, there is no co-ordinated system of ongoing monitoring in place. Furthermore, there is a failure to define specific targets. Without targets and quantified objectives it is not possible to relate the results of evaluation back to the scheme. The REPS and its sister programmes elsewhere are innovative schemes which will need to be appraised and modified if they are to realise their full potential (Hamell, 1999).
The need for clear objectives and verifiable targets cannot be overstated. These facilitate effective scheme design and objective-led monitoring, the results of which can then feed back into improved scheme design. It would take only a tiny proportion of the REPS budget to tackle this properly and thus secure the future of the scheme.
References
Bakker J.P. and Berendse F. (1999) Constraints in the restoration of ecological diversity in grassland and heathland communities. Trends in Ecology and Evolution14: 63-68.
De Snoo, G.R. and De Wit, P.J. (1998) Buffer zones for reducing pesticide drift to ditches and risks to aquatic organisms. Ecotoxicology and Environmental Safety41: 112-118.
Department of Agriculture, Food and Rural Development (2000). Rural Environment Protection Scheme. Specifications for REPS 2000. Government of Ireland Publications, Dublin.
Hamell, M. (1999) Environmental Protection Requirements for Agriculture - Perspective for the New Millennium. In: Proceedings of the 1999 REPS Conference 24-31. Teagasc publications, Dublin.
Kromp, B. (1999) Carabid beetles in sustainable agriculture: a review on pest control efficacy, cultivation impacts and enhancement. In: Invertebrate biodiversity as bioindicators of sustainable landscapes. Paoletti (Ed.), Agriculture, ecosystems and environment 74: 187-228.
Moonen, A.C. and Marshall, E.J.P. (2001) The influence of sown margin strips, management and boundary structure on herbaceous field margin vegetation in two neighbouring farms in southern England. Agriculture, Ecosystems and Environment86: 187-202.
Schmid, W. and Wiedemeier, P. (1999) Extensive Weiden bringen Vielfalt. Beweidung und Naturschutz - ein Widerspruch? Ornis. Zeitschrift des Schweizer Vogelschutzes SVS - Birdlife Schweiz3: 8-12.
Thiele, H.-U, (1977) Carabid Beetles in their Environments. Springer, Verlag, Berlin.
