Creating New Verges of Value to Wildlife - the importance of soil fertility - or lack of it

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