Creating New Verges of Value to Wildlife
The importance of soil fertility - or lack of it
An ecological approach to grass verge management
•
If we can control the amount grass grows in the first place, we will have less to cut
•
If we have less to cut, mowing should cost us less, and
we can spend more time on other jobs, and •
There will be more biodiversity because more species thrive in poorer soils
•
Drivers - austerity; enhancing biodiversity; Csequestration; response to public awareness & concern
What does soil fertility do to grassland?
Thick topsoil – coarse grasses dominate – high fertility – few gaps for germination
Thin topsoil / no topsoil – fine grasses & herbs – low fertility – plenty gaps for germination
Incorporate low fertility verges into scheme design: Weymouth Relief Road, Dorset (2009 – 2011)
SEED MIX
Low fertility - 15mm topsoil or just bare subsoil/mineral Wildflower seed hand sown
Crested Dog’s-tail Red Fescue Sheep's Fescue Yarrow Greater Knapweed Common Mouse-ear Rough Hawkbit Oxeye Daisy Bird's-foot trefoil Wild Marjoram Cowslip Yellow Rattle Salad Burnet Black Knapweed Wild Carrot Lady's Bedstraw Kidney Vetch Horseshoe Vetch Bee Orchid Pyramidal Orchid Autumn Lady’s Tresses Viper’s Bugloss Devil’s-bit Scabious Small Scabious Field Scabious
2013
2019
Date
Species
2013
133
2019
141
Ellenberg N Annual/biennials 5-9 1-3 Lost Gained
21 32
39% 25%
86% 54%
0% 35%
Conclusions: Vegetation is stabilising and becoming more closed Pioneer species are being lost Scrub is rare There are few non-natives Vegetation starting to resemble more semi-natural chalk grassland
2013
Small Blue total count on 2 sections of transect 313
158
87 49 11 2012
15 2013
31 2014
2015
41 2016
2017
2018
2019
2019
If you build it they will come ‌ Weymouth Relief Road Butterfly Monitoring 2000
35 30
1500
25 20
1000
15 10
500
5
0 2012 2013 2014 2015 2016 2017 2018 2019
Species accumulation
Total count per year
What are the savings in construction & management?
• Net saving of not having to place topsoil: £270,000 • Aftercare: notifiable weed control in Year 1 only • Annual maintenance: c. £500/yr (cf £2,700/yr)
• Occasional grazing of main slopes – 8 weeks in 10 years
B3350 Waddock Cross, Dorset
Verge used to be cut 8-9x per year to create max visibility at junction
Retrofitting low fertility
Verge topsoil replaced with chalk, sown with wildflowers - ÂŁ5,000
1 year later – wildflowers appearing, no management required at all
Crishall, Essex
Field Bindweed
Four-spotted Moth
Grey Carpet Moth
A11 - Croxton
Flixweed
Blandford, Dorset
Cut-and-collect in urban areas reduces fertility and creates a neat finish – fewer complaints in Dorset
Establishing wildflowers in amenity grass - reduce fertility first
Littlemoor Road, Weymouth
3 x cut & collect in 2017 reduces coarse grasses and favours fine grasses - this is mid-May in 2018
Littlemoor Road, Weymouth
Once regularly mown amenity grass, cut-and-collect started 2017, seeded in autumn 2017, now wildflower meadow in 2019
Conclusions • By viewing grassland verges as an ecosystem we understand how to control grass growth and increase wildflowers - low fertility is key to both • Grasslands good for wildlife are easy to create • Incorporate low fertility into scheme design from the outset for best effect • Changes to verge management are possible on any class of road • Cut-and-collect management reduces fertility and creates greater diversity • Working with the grain of nature saves time & money
Dr Phil Sterling Programme Manager, Building Sites for Butterflies Butterfly Conservation, Manor Yard, East Lulworth, Wareham, Dorset, BH20 5QP.
Email: psterling@butterfly-conservation.org Direct line: 01929 406030 www.butterfly-conservation.org/buildingsites