PfL Standards – Biodiversity and the Wider Environment

“Life begets life”; Grazing animals, insects, and the wider food web

By Pasture for Life Research Officers, Charlotte Wheeler and Jenna Thompson

(Photo: PfL certified Cotswold Beef)

Pasture for Life certification verifies that the certified animal, whether cattle, sheep, goat, or deer, has only ever consumed pasture and conserved forage over their lifespan. In this sense it certifies the animal, rather than the farm as a whole (as happens within organic certification). With that said, rearing livestock 100% on pasture requires excellent grazing and livestock management to ensure that stock have diverse and nutritionally complete diets without supplementing with grain or concentrates as is typical in most UK livestock systems. Whether our farmers certify because of ideological reasons or financial ones, the common result is that land is managed more sensitively, with a key emphasis on soil health, hydrological functioning, and biodiversity.

The debate over land-sparing and land-sharing, is often unhelpfully framed as a zero-sum binary, even though many people operating within the food and farming space recognise that we need to use every tool at our disposal to combat biodiversity loss, climate change, and pollution. However, while land-sparing and sustainable intensification have a role to play in future food systems it is important to recognise that land-sharing approaches have genuine biodiversity value in the wider UK landscape. In many countries, insect populations are in decline even within protected areas, suggesting that land-sparing approaches are not sufficient to support the recovery or insect populations on their own (1). In contrast, low-intensity agricultural practices provide the heterogeneity positively associated with invertebrate populations, and can provide connectivity between “wilder” areas, while also serving to buffer them from the effects of more intensively managed or developed landscapes.

Current status of biodiversity in the UK

While the overgrazing of livestock can absolutely have a detrimental effect along a range of indicators, it is also important to recognise the critical benefits that can be achieved through well-managed grazing, such as improved soil health (which increases resilience to periods of extreme weather), and generating food and livelihoods while supporting critical biodiversity recovery. This is a critical but often overlooked relationship. According to the State of Nature report (2019) there has been a 13% decline in species abundance since 1970 and the rate of decline has been steeper over the last 10 years. Since 1970, 41% of species have shown strong or moderate decreases in abundance and 27% have decreased in their distribution around the UK. Similarly, figures on the UK government website state that 63% of farmland bird species have shown a decline in numbers since 1970.

Many practices characteristic of modern conventional farming have had negative impacts on wildlife and contributed to this decline in biodiversity. The disappearance of mixed agricultural systems, including the decline of traditional rotations and the separation of arable/pastoral systems has contributed to the loss of plants, birds, mammals and insects from our landscapes. Other changes and practices that have had a negative impact on biodiversity include sowing crops in autumn rather than spring (which reduces food availability for birds), drainage, reseeding of native grasslands, switching from hay to silage, increased stocking rates, and anthelmintic use. Field sizes have increased, hedgerows have been removed, and their management (using hedge cutters annually rather than traditional hedge laying methods periodically) has further exacerbated the situation. Pesticides, synthetic fertilisers, and more efficient harvesting techniques have also significantly reduced habitat and food sources for wildlife (2).

Nature Friendly Farming

“Nature friendly” methods of livestock production and land management, such as those promoted by the Pasture for Life standards, are based upon the principle of ensuring wildlife habitats are no longer declining but are maintained and even regenerated. Many important and threatened species of native wildlife depend on grasslands as a habitat and food source, meaning their conservation can be supported through appropriate management. In contrast, it can be difficult to reverse biodiversity decline in intensive, high-input systems. Often, negligible increases in biodiversity are observed until there is a major shift to more extensive practices (such as in a land sharing approach). For example, in one study, reducing inorganic N fertiliser from from 250 kg ha−1 to 200 kg ha−1 had negligible effects on grassland biodiversity, with the biggest positive effect found in the final drop of 50 to 0 kg ha−1 (3).

Recently published research by Dr Lisa Norton, demonstrated that PfL approaches can be beneficial for grassland and wider ecosystems. Data from grassland plots managed by PfL farmers were compared to Countryside Survey (CS) plot data to assess the impacts of their practices on these variables. Results demonstrated that PfL plots were more species rich and contain more legume and forb species and lower proportions of perennial ryegrass than those on improved grassland (4). Higher species diversity in grasslands was linked to measures of soil health, such as soil moisture content, carbon and nitrogen content and biodiversity, including soil invertebrate abundance. Increased vegetation height was observed on PfL farms, which is known to be beneficial for biodiversity ranging from invertebrates, such as butterflies and bees, to mammals and birds. Vegetation height was also positively associated with soil moisture, C, N and total invertebrate abundance. This study shows that there are clear signs that grassland management, as practised by PfL members, is already improving the ecological condition of some UK grassland and wider ecosystems and that they are in better ecological condition than a large representative random sample of more intensive improved grassland across the UK.

(Photo: PfL certified Cotswold Beef)

Pasture biodiversity

Diversity can be measured at a variety of scales. On a regional level we can look at a range of farm types and habitat classifications, dependent on factors including underlying geology, soil type, altitude, and rainfall, and affected by human management. Intensive management including land drainage, ploughing, fertilisation, and reseeding with less diverse and more competitive grass mixes has reduced the diversity of many farmed landscapes. On a smaller, even field level, it can refer to not only the species richness of an area (i.e. the number of different species) but also the abundance (number of individuals within a species), or the structural diversity (the variety and range of plants heights and shapes).

Semi-natural grasslands and species rich pastures, i.e. hay meadows and pastures that are not intensively cultivated or fertilised, evolved as a result of centuries of low intensity farming and comprise of native strains of grasses and flowers. They can be among the most species-rich ecosystems in the world (7). In the UK, unimproved grassland communities hold very high conservation value due to their extreme rarity and fragmentation across the country, constituting only 1-2% of grassland (8), and experiencing a decline of at least 95% since 1940 following the introduction of synthetic fertilisers and intensive farming practices.. (9)

High levels of pasture diversity, whether in terms of species richness or physical sward structure, underpins wider grassland biodiversity by providing habitat, breeding, and forage opportunities for a range of species, as will be outlined below.

(Photo: PfL certified Cotswold Beef)

Invertebrates

Although invertebrate populations are not typically discussed with as much energy as greenhouse gas emissions, they are fundamental to ecosystem and agricultural health. Insects pollinate our crops, improve soil quality, and provide food for myriad other species including threatened farmland birds, bats, and other animals. The abundance and diversity of insects on a farm is therefore a key indicator or proxy for the health of the ecosystem overall, and land management practices which negatively impact insects are often associated with a loss of biodiversity more generally.

Several practices associated with high-intensity management have negative effects on invertebrates. Frequent mowing and the use of artificial fertilisers on pastures has had catastrophic impacts on insect populations, resulting not only in fewer insects, but also a reduced variety of species, and smaller overall insect size (10, 11).

Low-input management is often associated with the reverse relationship. Insect diversity is often (though not always) strongly linked with plant diversity, and the physical structure of the sward is important, with short swards or swards of a consistent height generally containing a lower abundance and reduced diversity of insects compared with taller ones (12, 13). Rotational grazing can be used to generate a variety of different grassland heights, ages and successional stages, thereby producing maximal variability, which may help maintain a larger number of species with different habitat requirements (14).

One of the key differences between mown and grazed grassland is that in the latter the behaviour of the grazing animal leads to greater structural variability in the sward. This is accomplished by either selective grazing, trampling and opening up of vegetation, seed dispersal, and/or nutrient cycling via dung and urine. The relative impact of each of these mechanisms will depend on the particular type of grassland and the aims of grazing management (such as productivity, encouraging diversity, or conservation) (15). For example, trampling may have a particularly important role in allowing species colonisation of grasslands where the goal is de-intensification.

We also know that cutting for hay causes a sharp decline in invertebrate populations because all habitat is removed at once, compared to grazing which allows insects the opportunity to escape into other parts of the pasture. However, it is equally true that continuous grazing of livestock on the same area, throughout the growing season, has a negative impact on insect populations due to the reduction in habitat and forage sources available.

(Photo: PfL certified Cotswold Beef)

Dung

A landmark study of cowpats in 1954 estimated that each animal, kept outdoors year round produced around 6,000 insects per day, or nearly 2.2 million insects per year. This benefit to birds, bats, and the wider food web is obviously completely undermined by the routine use of anthelmintics. Pasture for Life standards require Fecal Egg Counts to be undertaken before anthelmintics are used in order to determine their necessity, and rotational grazing often reduces the prevalence of intestinal parasites (16) in grazing livestock as they are moved through through pastures, interrupting the life cycle of common intestinal parasites while still providing critical food sources for numerous invertebrate species.

Birds

Almost a third of the bird species designated as Species of European Conservation Concern are dependent to some extent on agricultural grasslands for both nesting and foraging. However, the structurally diverse and species-rich swards many depend upon have been largely replaced by relatively dense, fast-growing and structurally uniform swards, dominated by competitive species, which are well suited for high yields per hectare and silage making.

The most important direct effects have been deterioration of the sward as nesting and wintering habitat, and loss of seed resources as food. Pesticide use directly impacts insect populations, while overall homogenisation of the farmed landscape does so indirectly.

Reduced insect diversity and abundance reduces food sources of insect-eating bird species, while increased mowing and grazing intensity reduces forage for seed-eating birds as plants are defoliated before they have a chance to flower and set seed. Short uniform swards offer poor shelter and camouflage from predators, and increased mowing intensities and trampling by stock destroying nests and young. Land drainage has dramatically reduced habitat and feed sources for wetland species. These issues have led to a decline in bird populations in both lowland and upland areas (17).

One study suggested that mosaics of fields managed as short-term leys and permanent pastures with low intensity grazing over autumn and winter could provide the combination of heterogenous sward structure, area of bare earth and presence of some seeding plants necessary to maximise the opportunities for a range of bird species to use a given area of grassland throughout winter (18).

(Photo: PfL certified Cotswold Beef)

Conclusion

As described above, the relationship between pasture diversity, and invertebrate and bird populations are difficult to extricate from one another; without healthy and diverse populations of one category, you do not have healthy and diverse populations of the others. Biodiversity cannot be increased without improving diversity at all scales; the more different types of ecosystems, such as wetlands, arable, grassland, orchard etc, and the more diverse those systems are in themselves, the greater the variety of available habitat and food for a range of species, and the more life that will be found as a result.