Biodiversity Net Gain

Biodiversity net gain is something that all landowners should be considering at every opportunity.

Biodiversity net gain (BNG) is a key strategy outlined in the government’s Environment Act (2021). The government asserts that it is fundamental in achieving our goal of halting the decline in species abundance by 2030, while also promoting the development of more attractive communities and new housing.

How can farmers achieve BNG?

Farmers have three methods to achieve BNG: on-site, off-site, and the purchase of biodiversity credits, which should only be used as a last resort. On-site BNG involves improving and restoring biodiversity within the development site’s red-line boundary. Off-site BNG involves purchasing biodiversity units, which can be combined with on-site improvements to achieve 10% BNG. If the required net gain cannot be obtained through a combination of on-site and off-site measures, farmers must purchase statutory biodiversity credits from the government. It is important to remember that BNG cannot be achieved if the development involves the loss of an irreplaceable habitat.

What do farmers have to do?

To comply with the new BNG mandate, there are three main requirements for farmers.

Firstly, it is necessary to register a biodiversity gain site on the government’s register if paying a landowner or landowners to create or improve their habitats.

Secondly, consulting an ecologist is vital, who will measure the biodiversity units of existing habitats on the farmer’s land using the biodiversity metric and then suggest ways to increase biodiversity. Note that the LPA has the right to reject calculations that weren’t crunched by a competent individual.

Lastly, farmers must sign a legal agreement with the local authority indicating how biodiversity will increase over a minimum of 30 years.

How do statutory biodiversity credits work?

Statutory biodiversity credits are a final option when on-site and off-site biodiversity gain cannot be achieved. It is worth noting that the terms “biodiversity unit” and “biodiversity credit” are occasionally used interchangeably, despite the fact that within the BNG framework, a unit is a means of measuring biodiversity, whereas a credit is something that may be obtained from the Secretary of State. The proceeds from these credits will, reportedly, be reinvested in biodiversity.

Bees & Pollinating Insects – Perennial crops as a source of food for bees.

Willow is a significant source of nectar and pollen for insects, including bees and butterflies. Recent worldwide research indicates that 40% of insect species are experiencing “dramatic rates of decline”. In the UK, studies reveal declines in butterflies, moths, beetles, bees, and hoverflies. These insects are critical pollinators, and their decline can have devastating consequences for entire ecosystems. Insects are doubly vital as they serve as both pollinators and a crucial food source for many other creatures such as birds, bats, amphibians, and reptiles. Furthermore, studies demonstrate that more insects live on willows than on any other tree species in the UK.

An abundance of pollen is required early in the year which makes Willow a very important plant for honey bee nutrition.

Willow trees in Great Britain are a crucial source of pollen and nectar for Honey Bees, making them an essential forage plant. The Willows are dioecious, with male and female catkins on separate plants. Both sexes offer nectar, with the males producing pollen – also known as bee bread – in tremendous amounts. This abundant source of pollen is particularly important at the beginning of the season when colonies are recovering from winter and other pollen sources are scarce. Honey Bees require a significant amount of pollen since it serves as a primary source of protein, fat, vitamins, and minerals. The colony’s demand for pollen is linked to the amount of unsealed brood present, and without pollen, nurse bees can’t produce sufficient brood food. Pollen-rich in protein is necessary for the growth, development, and tissue repair of bees. Bees have the ability to distinguish between pollens by their color and odor but can’t differentiate between their nutritional contents. Pollen is also indispensable to the orderly development of the honey bee’s glandular system while still a house bee. A strong colony of honey bees at its peak of brood rearing requires about half a pound of pollen daily.

This is a list of tree species and their associated insect species populations.

Tree Species	No. of Insect Species
Oak	284
Willow	266
Birch	229
Hawthorn	149
Poplar	97
Apple	93
Pine	91
Alder	90
Elm	82
Hazel	73
Beech	64
Ash	41

Source: T.R.E. Southwood, “The Number of Species of Insect Associated with Various Trees,” Journal of Animal Ecology, Vol. 30, No. 1, pp. 1-8.

Birds – Perennial cops can provide extensive habitats for many different bird species.

Numerous studies have been conducted on SRC Willow and SRC Poplar plantations to count bird species, monitor behaviours, and produce comparisons between energy crop and arable farming. These studies reveal that both Willow and Poplar are highly attractive to numerous bird species, with SRC Willow being particularly exceptional. The referenced study suggests that SRC Willow attracts more species than arable or managed grassland and concludes that SRC can significantly increase diversity. However, it emphasizes that the design and management of SRC plantations are crucial in maximizing benefits to birds.

The study conducted in Yorkshire has shown an impressive list of species observed in SRC Willow, including some considered endangered in the UK, such as Woodpigeon, Dunnock, Robin, Blackbird, Song Thrush, Whitethroat, Chiffchaff, Willow Warbler, Long-tailed Tit, Blue Tit, Great Tit, Blackcap, Magpie, Chaffinch, Goldfinch, Yellowhammer, and Reed Bunting. Migratory species like Snipe, Woodcock, and Fieldfare were also surveyed and counted. Additional observations include predators like Red Kites, Barn Owls, and Tawny Owls.

Many experts suggest that to achieve maximum biodiversity, special attention should be paid to the SRC plantation’s surroundings. Feeding preferences of many bird species highlight the importance of planting SRC near established woodland, rather than deep within the wood.

Bird species that benefit from perennial crops -

Mammals – Small mammals can be found in many perennial crops.

Studies indicate that energy crops have demonstrated significant appeal among mammalian species. An observation of no fewer than ten species within SRC plantations corroborates this fact.

Small mammal species, including voles and bats, are currently facing high levels of threat. However, energy crop plantations have proven to be a source of beneficial habitats for these species, providing food for owls in turn. To promote biodiversity among mammals, it is recommended to continue developing hedgerows and margins surrounding energy crops, as is done for birdlife.

Flora – Encouraging biodiversity by allowing ground cover to flourish

Biodiversity is enhanced by the presence of suitable habitats. By promoting the growth of beneficial ground cover around the crop stems, a multitude of small creatures can establish their homes with ease. Consequently, this attracts predators and fosters the development of tiers in the biodiversity pyramid.

Remarkably, more than 150 species of plant have been observed growing in SRC willow across various locations in England. These provide a vital source of food for various insects and butterflies, along with their predators. Besides, an increase in ground flora variety can also help with weed control by stifling unwanted species. Furthermore, floral diversity promotes the arrival of predatory invertebrates that control pest species.

An intelligent selection of ground cover can further facilitate grazing by suitable livestock. Sheep, pigs and chickens can all flourish in an SRC or SRF energy crop plantation.

Agroforestry

Poplar is the obvious choice for agroforestry use alongside livestock to generate an income, energy & biodiversity net gain.

Find out more