Biodiversity – an introduction
If you’re on this page, you probably already know what a tough time Britain’s wildlife is having: 78% fall in flying insects since 2004 (Buglife); 97% loss of species rich grasslands since the 1930’s (Plantlife); 54% decline in wildflowers since 1970 (State of Nature Report 2023) …. the list goes on.
But we can make a difference – in our green spaces, gardens, parks, verges and public spaces. Recent research by the University of Sussex showed small scale community gardening increases biodiversity whilst producing crop yields comparable or higher to large-scale conventional farms. A study in Saltdean revealed that areas of grass in a public park left to grow longer and cut once a year led to a fifty times increase in insect life, with 97% of park users favouring the new management regime.
When we asked local groups how important helping wildlife and increasing biodiversity was to their work, 85% said it was essential, and 15% said very important. If you’re new to this subject, or would like a refresher, please read on for some key terms and ideas.
Biodiversity
Biodiversity means the abundance of different species living in one area – so the more different species, the higher the biodiversity. Consider a typical green urban space with mown grass. Below the surface, there are a multitude of micro-organisms. Then we have several species of grasses, some mosses, some wildflowers such as dandelions, daisies, clover and plantains – although these will be mown short and not usually allowed to flower. Living in the grass and soil you’ll probably find invertebrates such as worms, snails, ants, spiders and flies. The occasional bird might fly through, but they’re unlikely to stay for long as there’s little shelter and not much to eat! But allow the grass to grow longer, and suddenly biodiversity increases – insects will find shelter and food, and a place to lay eggs and reproduce. Birds and amphibians (if there’s a pond nearby) will find food and a hiding place from predators. Under the surface of the soil, the longer roots of the grasses will start to increase carbon capture and improve soil health. Then imagine if you add flowering plants, shrubs and trees: you’re providing food for bees, butterflies and a range of pollinating insects, as well as a safe perch and even a nesting site for birds. Leaves and leaf litter provide food for an increasing range of different creatures. Add some wood piles, nest boxes, bug houses and bee hotels and the biodiversity of this green space starts to increase exponentially!
Resilience
In this context, resilience refers to the ability of species and environments to cope with the more extreme weather patterns we’re experience due to climate change, eg: longer periods of drought in summer; water-logging in winter; warmer winters and periods of unusual weather patterns, as well as the movement and introduction of pests and diseases from abroad. As well as considering how well individual species can manage in these conditions, we can also increase resilience by planting a range of different plants, so that if we’re hit by an unexpected frost, or a wet winter, not everything will be affected.
Native versus non-native
Native plants are those which occur naturally in the UK, and haven’t been introduced by humans. Native plants are generally considered very good for biodiversity and wildlife: some insects will only eat one type of plant!. But native plants are not always appropriate for every situation or location.
Non-native or exotic plants usually refer to plants which come from the Southern hemisphere. They can be very useful for providing nectar and pollen for insects, and extending the flowering season – ie it isn’t the case that wildlife-friendly planting means only using native species.
So what to do? The latest research indicates that planting a mix of native and non-native flowering plants can be more beneficial than just native plants. The benefit of planting non-natives is that they often flower when natives don’t, thus providing important pollen and nectar for pollinators.
Using mix of native and non-native can also be useful in terms of public opinion. In the Friends of Sutton Downs rain garden, ‘people-pleasing’ exotics were deliberately chosen in addition to those which are wildlife-friendly.
Near-native plants or near-native species
These are plants that are similar to our native species. For example, honeysuckle is a native species, but you can also find near-native honeysuckles that have been bred for bigger flowers, variegated leaves etc. An example is the honeysuckle ‘Graham Thomas’. Often these plants tick the boxes of being both good for wildlife and attractive to people – but do your research for each plant, as they’re all different!
Invasive
Sometimes known as ‘thug’ plants, in horticulture, this refers to species which take over and can be difficult to control. Some invasive non-native plants cause so many problems that allowing them to ‘escape’ from a garden is illegal.
Single or double flowered?
A single ring of petals means there’s plenty of pollen and nectar in the centre of a flower for a visiting insect. When plants have been bred to have fancy double rings of flowers, they tend to provide less (or no) food. Of course, it’s not quite as simple as this but it’s a good rule of thumb to start with.
Pollinators
A pollinating insect is one which conveys pollen to a plant and so allows fertilisation. Three quarters of the world’s flowering plants and 35% of the world’s food crops need animal pollinators to reproduce. We tend to focus on bees and butterflies, but pollinators include an incredibly diverse group, including wasps, moths, hoverflies, flies and beetles. And don’t forget all the other invertebrates which might not be pollinators, but still provide essential services to our ecosystem!
Pollen and nectar
Flowers provide both pollen and nectar to pollinating insects. Pollen is high in protein, and helps them produce eggs and feed their young. Nectar is a sweet substance, and provides the insects with energy and vitamins. Insects don’t care where pollen and nectar come from – native or exotic plant. However, some creatures rely on the leaves and vegetative parts of native plants for food and to complete their lifecycles, which is why a mixture of native and non-native plants can be a good choice for helping wildlife.
Biodiversity Net Gain
Biodiversity Net Gain is a new approach to land management (introduced in February 2024) for developers, land owners and local authorities that aims to deliver measurable improvements for nature by creating or enhancing wildlife habitats. All developers must deliver a BNG of 10%.