How to Rewild

Modified Grassland

Habitat Management Plan

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Modified Grassland
Habitat Guide

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Modified Grassland is the second most common habitat type in the UK by area, after Arable & Horticulture. This includes everything from football pitches to grazing pastures, and your lawn is the same kind of habitat, which should be managed in the same way, though it technically falls into the Built-up Areas & Gardens category. Most Modified Grassland is very low in biodiversity, due to inputs of fertilisers and pesticides, drainage, occasional ploughing and overgrazing or intensive mowing.

This habitat is dominated by rye grass, but may also have abundant growth of clover, and ‘weeds’ like buttercups, daisies, dock and dandelions. The biodiversity supported by Modified Grassland is very low, compared to almost any other ‘natural’ habitat type. However, this habitat plays an important role in recreation, shared community spaces and agricultural productivity. The loss of high quality farming land to rewilding is likely to create a knock-on effect on biodiversity elsewhere.

With that in mind, degraded pasture is ideal for rewilding projects, as land is cheap, and interventions shouldn’t damage the limited existing biodiversity. An alternative solution is switching the land from pasture to agroforestry, which will increase the benefits to nature while diversifying income streams and restoring soil health.

Sub Habitats

Nutrient-enriched grassland/lawns, typically found in agricultural pastures, and in urban settings like parks, gardens and road verges.

Value

Modified Grassland is often the surface for recreation in parks and on sports pitches. Here, the lush, consistent growth is valuable for protecting the soil against erosion, and a more environmentally-friendly solution than artificial alternatives like astroturf and tarmac. The grass can soak up nutrients and pollutants, like dog excrement and road runoff. However, the use of fertilisers and weedkillers can also create negative impacts on other local habitats, particularly watercourses.

In farmland, a near-monoculture crop of rye grass and clover is typical for many pastures. This has very low value for biodiversity, though the clover does provide nectar, which can support some limited pollinator populations. The presence of livestock creates some opportunities for invertebrates, and birds like starling, meadow pipit and oystercatcher. The primary value of grass here is as a crop, and its weight is converted into animal products in the form of milk, cheese, wool, leather etc, and meat.

Like Arable & Horticulture, Coniferous Woodland, and Built-up Areas & Gardens, it is difficult to place an objective value on Modified Grassland. While biodiversity is low, the loss of this habitat could have lasting negative impacts on the local community, health, culture and economy. Land managers who don’t think about these effects and come up with ways to make up for any changes, are likely to damage their reputation.

Rewilding project
Modified grassland is often the starting point for a rewilding project, and is suitable for tree planting.

Protect

When agricultural productivity is lost in one place, it is usually made up elsewhere – our need for food creates demand for more farmland. We call this the ‘farmland footprint’ – it’s why we recommend that pasture with a DEFRA agricultural land classification of 1 or 2 remains in use as farmland. Replacing 1 hectare of high value farmland could mean losing multiple hectares of biodiverse land elsewhere in the world.

On highly productive farmland, biodiversity can still be enhanced in a number of different ways. Regenerative agriculture, rather than rewilding, offers solutions like herbal leys, agroforestry and mob grazing which mimic more natural meadows and restore soil health.

Agroforestry

Agroforestry is increasingly recognised as an important aid to farmers, with benefits for livestock health. Planting orchards, or in-field shelter belts, and allowing existing hedgerows to thicken out into denser wedge shapes will create shade and protection from the elements. This may result in improved milk yield, reduced heat and cold stress effects, and improvements to the quality of meat production.

Alley cropping systems take agroforestry further, by subdividing existing fields into strips wide enough to take standard farming machinery. These 24m wide pasture strips are then subdivided by rows of fruit, nut, coppice or timber trees, which can produce a secondary product. The tree strips are protected from grazing by a single high-tensile electric fence wire, or two strands where calves are present. This system of alleys, with ends that can be quickly closed and opened, also allows for mob grazing of larger fields, improving the quality of the pasture. A good example of this is at Eastbrook Farm near Swindon.

Alternative Grazing Systems

Mob grazing means changing the frequency and intensity of grazing, from a near-constant moderate pressure to a very infrequent, high intensity system. Small sections of land are grazed for a day, or a few days at a time, by large herds, which maximises the use of every square metre. The vegetation becomes trampled into the ground, and after the herd moves on, this rots down, enriching soil organic matter. By moving livestock frequently, there is a lower parasite load and the nutritional quality of forage increases.

Another method for improving the productivity and biodiversity of Modified Grassland pasture is sowing a herbal ley. This is a diverse mix of native and non-native grasses and wildflowers, which enrich the soil, improve the quality of forage and increase drought resilience. Deep rooting perennials can also be used to bring up valuable minerals that lie below the surface, improving livestock health. Supplementing this grass with tree fodder in the form of willow leaves and branches from pollarded trees within the pasture can further improve the health and biodiversity benefits of the system.

Beyond the Farm

When maintaining a Modified Grassland system outside of the farm, moderate density livestock can be valuable for creating more diversity. However, on sports pitches and walking paths (especially accessible routes), the use of animals will create a dangerous, uneven surface.

If livestock are an option, cattle and horses are usually better than sheep here, or horses alone as they browse less selectively, creating a more diverse sward which isn’t overwhelmed by ‘horse weeds’ like dock. Their hooves and activity create bare patches and tussocks which are ideal for wildflower seeds to germinate. If the consistency of the surface is not an issue, pigs are ideal at low density, particularly in semi-wooded areas, as they turn over the turf and create wallows, which are breeding habitat for amphibians and invertebrates.

Annual Management

Grazers will maintain a variable sward height, which benefits the little biodiversity that can be found here. Fertilisers increase the dominance and density of grass, and the sward height, maintaining the existing Modified Grassland state. Grazing typically takes place from late September to December – or from June if the site is not mown – at a low-enough stocking density that the sward height stays above 5cm.

If you rely on mowing alone, a single annual cut may not be enough to maintain this habitat due to the vigour of grasses. A single full cut to 5cm height should be taken in August or September. In a two cut system, the first cut is generally taken in February or March, and the last in September or October. On dry land, more cuts may be possible without degrading the habitat. In every system, the cut grass must be raked off and removed from site, or composted elsewhere on site, to avoid choking fresh wildflower growth and creating a build-up of nutrients. More regular cuts will usually result in a monoculture of vigorous grass (a low biodiversity lawn). 

Cows in orchard silvopasture
Modified grassland may be highly productive land, suitable for conversion to agroforestry, like mixed orchard/pasture.

Restore

Other types of grassland may have been converted to Modified Grassland by agricultural intensification. This creates a lush sward that typically reverts to agricultural weeds like thistles, ragwort, dock and nettles when mowing or grazing stops. Converting Modified Grassland back to Neutral, Acid or Calcareous Grassland is often possible – follow the relevant steps in the Restore section of those pages.

Beyond grasslands, other habitats may also be a goal if you have them in your local area. Any kind of habitat work which increases the variation in height and structure of vegetation tends to result in more biodiversity – a mosaic of scrub, woodland and ponds is ideal. The soil type on your land must be suitable for the habitat you’ve chosen to restore – here are some of the possibilities:

 

Each of these habitats require a different approach, but many may benefit from nutrient-stripping, as the artificially-high levels of nutrients in Modified Grassland soil can make even a woodland develop unnaturally.

All of these methods involve knocking back vigorous grass growth, as grass outcompetes wildflowers. Grass typically grows faster on ground with high levels of fertiliser. Fertiliser contains multiple nutrients – nitrogen (N), phosphorus (P) and potassium (K); to get back to a diverse grassland habitat, we’ll either reduce their concentration or make it harder for plants to access them.

1 – Removing Inputs

Artificially high levels of nutrients in the soil will naturally decline over time, as they wash out and are taken up and ‘locked away’ in plants. That’s why farmers must re-apply fertiliser every year. So, one of the first things to tackle is removing any artificial inputs. This includes supplementary feeding of livestock (e.g. grain troughs) and runoff from neighbouring farms. By avoiding fertilisers/muck-spreading, stopping supplementary feeding, and preventing incoming runoff, you should see a slow decline in soil nutrients. However, it is possible that there may still be another input which hasn’t yet been identified, like high atmospheric deposition, enriched floodwater, or even dog excrement!

2 – Sowing Hemiparasitic Plants

These plants attach to the roots of grass and suck nutrients out directly, reducing the vigour of the grasses. But these short plants do poorly in habitats with a tall sward, as they only thrive when they can get enough light. So, managing the habitat with grazers and/or mowing strategically, to avoid chopping them before they set seed, is necessary for successful establishment. They also need bare soil to germinate, so scarifying the grass before scattering seed gives them a good head start.

3 – Grazing

In general, grazing your land with livestock should reduce nutrient levels over time, for a few different reasons. The animals will excrete nutrients into the soil, where they are washed away, and nutrients are released as volatile compounds into the air; they’re removed in animal products like wool and milk; and also in their meat. The overall impact varies a lot depending on the livestock, site, soils, climate etc. This method is slow but steady, and creates biodiversity along the way, as the grassland will be more varied in height than if you use a mower. Grazing also has the added benefit that it ‘masks’ the effects of nutrient-enrichment – livestock prefer eating taller, dominant plants like grasses, allowing shorter wildflowers to get established, provided that the area isn’t overgrazed.

4 – Mowing

Over a decade or two, you’ll find that consistent cutting and removal of hay should reduce the available nutrients in the soil and create a more diverse grassland community. However, in the short term, frequent mowing can create more vigorous grass growth, especially if the ground is rich in nutrients. Mowing can also remove plant seed heads before they have a chance to scatter onto the soil. It’s a balancing act, finding the right timing and frequency – twice a year is typically recommended for nutrient-enriched sites. The hay must be removed each time, to prevent a steady build-up of nutrients and choking-out fresh growth.

5 – Rooting

Fertilised grasslands, and those which have been intensively grazed or mown for a long time are very resistant to change. The sward will have become dense and matted, and it will take many decades to ‘reset’ this habitat. We can help this process along by introducing pigs, which turn over the turf in patches, just like our native Wild Boar. This knocks back the grass and allows seeds below the soil to germinate – it is likely to lead to a flush of agricultural ‘weeds’ at first. These will add structure and biodiversity, and are eventually succeeded (with regular grazing/mowing) by a more diverse collection of wildflowers and grasses. Without pigs, we can have a similar, though slightly less effective impact, using a rotavator. Note that this process – with or without pigs – leaves the grassland tussocky and uneven – it’s great for biodiversity, but not for recreation.

6 – Soil Stripping

Nutrients are concentrated in plants and the topsoil, so we can strip off this top layer of turf to solve the problem. With deeper soils, soil stripping may be easy to achieve, but a high water table could lead to waterlogging of stripped areas. And even if it is achieved, this will have a significant medium term carbon footprint, and will likely lead to runoff, soil compaction and loss of plant diversity. Removing strips of soil in rotation, will allow plant seeds and the soil community to transfer slowly from healthy grassland to recovering bare ground. While this method is very destructive, it is the only proven system for significantly reducing nutrients in one shot.

Follow-up

Nutrient-stripping is only the first step in restoring the previous habitat or creating a new one from scratch. While trees and scrub could return naturally from the seedbank in the soil, this is unlikely to happen very quickly in the centre of open fields, especially if they are far from a woodland or hedgerow seed source. It’s worth identifying the previous habitat from old maps, and from the plants which appear in the first year or two of rewilding, then taking a look at the Restore section on the relevant habitat page to learn more.

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