NB3 Extent and condition of natural landscape connections: hedgerows and ponds

Hedgerows

Extent

In 2007 the length of hedgerows in Scotland was 21,200,000 km, a decrease of approximately 7% since 1998.

Condition

In 2007 there were 14.7 vegetation species per Hedge Plot (the size of these plots is 10 metres by one metre) in Scotland.  This is a statistically significant decrease of 22% between 1998 and 2007.  There were corresponding decreases in the presence of species used for food by farmland birds and butterfly caterpillar food plants over the same period.  Meanwhile there was an increase in grass species associated with shaded conditions.

Table 1: Hedgerow condition values and trends

In addition, in 2007:

• There were an average 2.2 woody species per 30m section of hedge, a statistically significant increase from 1.8 species in 1998;
• 36% of all managed hedges were in good structural condition
• Only 6% of managed hedges on arable land were in good structural condition with appropriately managed margins.

Ponds

Extent

In 2007 there were 198, 000 ponds in Scotland.  This is a 6% increase in the number of ponds since 1998.

Table 2: Trend in pond numbers

Condition

The 2007 Countryside Survey provides the baseline condition of ponds across Scotland, based on their plant communities.  In 2007 Scottish ponds supported an average of 9.6 wetland plant species per pond. Only 9.9% of ponds met Priority Habitat status; all of those were based on the ‘presence of rare plant species’ quality criteria for plants. (To qualify for Priority Habit status based on the diversity of plant species, a pond has to support at least 30 wetland plant species (JNCC, 2008)).

Hedges

Future surveys may see improvements in hedgerow extent and/or quality due to the effect of incentives. The Scottish Rural Development Programme (SRDP) Management of Hedgerows Option was temporarily suspended in 2011, following contributions of over £32m to creation and management of 2,655km of hedgerows to benefit biodiversity.

SRDP Options for 2015-2020 are due for publication later in 2015. It is not expected that there will be substantive changes to the options available for Hedgerows; however they will be spatially restricted to the areas where they can achieve the highest impact in terms of biodiversity and water quality. It is therefore likely that funding will not be available in parts of the Highlands that have benefitted in the past.

Ponds

Recent environmental legislation imposes requirements to protect water bodies that will hopefully lead to improvements in pond condition. The UK Biodiversity Action plan (BAP) included ponds as a Priority Habitat in 2007 for the first time.  

Hedgerows

Extent

As farming intensified between the 1940s and 1980s many hedges were removed to create larger fields or were replaced by fencing.  The use of pesticides and fertilisers in intensively farmed areas also contributed to a loss of biodiversity in boundary features (Norton et al, 2009).  The percentage of newly planted hedges picked up in the survey is likely to be a reflection of the take-up of hedge planting initiatives.  However the overall decline in the extent of hedgerows may reduce species ability to track ‘climate space’ in a changing climate.

Condition

The increase in the mean number of woody species per 30m length of hedgerow between 1998 and 2007 probably results from agri-environment schemes that encouraged the planting of new species rich hedgerows, and also the Countryside Survey policy to sample new hedges in 2007 that resulted in a number of Hedge Diversity Plots being located on new hedges in Scotland (Norton et al, 2009).  If the increasing number of woody species does reflect an improvement in hedgerow condition, this could indicate both that the hedgerows are more resilient to climate change and that species utilising them to move through the landscape are better able to disperse.

Ponds

Extent

In the middle years of the 20^th century ponds were lost due to agricultural intensification and pollution. The increased number of ponds recorded in 2007 may in part be due to particularly wet conditions during the survey period that year. In the Lowlands some of the increase may be a result of pond creation in response to incentives. This increase might help reverse earlier losses and benefit biodiversity, provided their condition is good enough (Norton et al, 2009).

Condition

As pond condition data was not recorded prior to 2007, only baseline data is available. The average of 9.6 wetland plant species per pond recorded in 2007 is relatively low (for example, for Priority Habitat status the species richness criterion requires 30 or more wetland plant species). However, around two-thirds of all ponds, or lochans, surveyed are situated in the Intermediate Uplands and Islands. Lower diversity would be expected in many upland habitats which are low in nutrients (Norton et al, 2009). It is possible that both nutrient pollution from agricultural run-off and water body isolation due to earlier pond losses may still be negatively impacting pond condition (Norton et al, 2009).

Sample sizes, definitions and classification of hedgerows changed in the 1998 survey.  Data for 1990 has been adjusted for comparison.

It is probable that more of the surveyed ponds would qualify for Priority Habitat status if additional criteria, such as the presence of invertebrates and amphibians were also assessed. This means that the current Countryside Survey only provides a minimum estimate of the number of Priority Habitat Ponds in Scotland and a baseline for comparison with future surveys.

Hedgerow Diversity Plots were not recorded before 1998.  The majority (56/60) of Hedge Plots are within the Lowlands region.

Brown, I et al (2012) Climate Change Risk Assessment for the biodiversity and ecosystem services sector. UK CCRA https://www.gov.uk/government/policies/adapting-to-climate-change

Carey, P.D., Wallis, S., Emmett, B.A., Maskell, L.C., Murphy, J., Norton, L.R., Simpson, I.C., Smart, S.M. (2008) Countryside Survey: UK Headline Messages from 2007. NERC/Centre for Ecology & Hydrology, 30pp. (CEH Project Number: C03259).

Carey, P.D.; Wallis, S., Chamberlain, P.M., Cooper, A., Emmett, B.A., Maskell, L.C., McCann, T., Murphy, J., Norton, L.R., Reynolds, B., Scott, W.A., Simpson, I.C., Smart, S.M., Ullyett, J.M. (2008) Countryside Survey: UK Results from 2007. NERC/Centre for Ecology & Hydrology, 105pp. (CEH Project Number: C03259).

Norton, L.R., Murphy, J., Reynolds, B., Marks, S., Mackey, E.C. (2009) Countryside Survey: Scotland Results from 2007. NERC/Centre for Ecology & Hydrology, The Scottish Government, Scottish Natural Heritage, 83pp. (CEH Project Number: C03259).

Williams, P., Biggs, J., Crowe, A., Murphy, J., Nicolet, P., Weatherby, A., Dunbar, M. (2010) Countryside Survey: Ponds Report from 2007. Technical Report No. 7/07 Pond Conservation and NERC/Centre for Ecology & Hydrology, 77pp. (CEH Project Number: C03259).

JNCC (2008) UK Biodiversity Action Plan Priority Habitat Descriptions: Ponds. Available at: http://jncc.defra.gov.uk/page-5706 (accessed March 2015)