Pollinators & Biodiversity FAQs
Enhancing green spaces in London where all natural pollinators can thrive, and their habitats can be enjoyed by all.
Pollinators & Biodiversity FAQs
1. What are pollinators?
Pollinators are insects and other animals that transfer pollen between flowers, enabling plants to reproduce. In the UK, the main pollinators include bumblebees, solitary bees, butterflies, moths, hoverflies, beetles and wasps. They play a vital role in supporting food crops, wild plants and overall ecosystem health.
2. Why are pollinators important in cities?
Cities may not seem like natural wildlife havens, but they can support high pollinator diversity. Urban pollinators help maintain green spaces, support fruiting trees and plants, and increase biodiversity. They also improve the resilience and beauty of parks, gardens and community spaces.
3. Which pollinators live in London?
London is home to a wide range of pollinator species, including:
- Bumblebees such as buff-tailed (Bombus terrestris), red-tailed (Bombus lapidarius) and white-tailed (Bombus lucorum)
- Solitary bees including red mason bees, leafcutter bees and numerous mining bee species
- Hoverflies — over 280 species are recorded in the UK, many of which occur in London
- Butterflies such as the holly blue, red admiral and small tortoiseshell
- Moths and beetles that also contribute to pollination
Many species thrive in parks, gardens, balconies, roadside verges and railway embankments.
4. Are pollinators declining in the UK?
Yes. Many wild pollinators face long-term decline due to habitat loss, reduced floral diversity, pesticide use, disease and climate change. Some species are stable or recovering locally, but overall trends show sustained pressure — particularly on solitary bees, some bumblebee species and many butterfly species. The UK has lost significant numbers of pollinator species from large parts of their former ranges since the mid-twentieth century.
5. What is the biggest threat to urban pollinators?
The main challenges for urban pollinators include:
- Fragmented and limited habitat, with green spaces too small or too isolated to sustain populations
- Poor planting choices and lack of year-round flowers
- Overuse of pesticides, including herbicides that remove wild food plants
- Loss of ‘messy’ natural features such as bare soil, dead wood and rough grass
- High numbers of managed honeybee hives competing for limited floral resources in areas that cannot support them
6. How can small gardens help pollinators?
Even the smallest patch can make a meaningful contribution. Planting nectar-rich flowers — especially native species — provides essential food. Leaving some areas undisturbed creates nesting opportunities. Window boxes, planters and balconies act as important stepping stones in the wider pollinator network across a city.
7. Do pollinators need large green spaces?
Large spaces help but are not essential. Pollinators use networks of small, scattered habitats — gardens, balconies, roadside verges, school grounds and community courtyards. Connectivity between these spaces is often more important than any individual site’s size.
8. How do pollinator pathways work?
Pollinator pathways are routes of connected habitat that allow pollinators to move safely through the environment. By linking parks, gardens and community sites with nectar-rich planting, pathways prevent the isolation of populations and improve feeding, nesting and breeding opportunities. PLT’s work in London focuses on building and strengthening these connections.
9. What plants are best for city pollinators?
Urban-friendly plants that consistently support pollinators include:
- Lavender
- Verbena bonariensis
- Sedum (ice plant)
- Scabious
- Catmint (Nepeta)
- Wildflowers such as knapweed, bird’s-foot trefoil, ox-eye daisy and wild marjoram
The key principles are variety, a preference for native species, and flowers available across all seasons from early spring to late autumn.
10. Are invasive species harmful to pollinators?
Some non-native invasive species can reduce the diversity pollinators depend on by outcompeting native wildflowers and spreading aggressively through habitats. However, not all non-native plants are harmful — many provide useful nectar and pollen. The concern is specifically with invasive species that spread uncontrollably and displace native vegetation. Planting native or non-invasive species is generally the safest approach.
11. What is the difference between a bumblebee and a solitary bee?
Bumblebees are social insects that live in colonies, typically of 50–400 workers headed by a queen. They are large, furry bees that are active from early spring, when new queens emerge from hibernation, through to autumn. Solitary bees, by contrast, do not form colonies — each female builds and provisions her own nest independently. The UK is home to around 250 species of solitary bee, ranging from the familiar red mason bee to tiny mining bees. Both groups are important pollinators, but they have very different life cycles, nesting requirements and seasonal activity patterns.
12. Why are solitary bees described as more efficient pollinators?
Solitary bees are often described as more efficient pollinators per visit than honeybees. This is partly because they carry pollen in a dry form on specialised hairs (the scopa), which tends to be deposited more freely on flower stigmas. Honeybees moisten pollen with nectar and pack it tightly into pollen baskets, making it less likely to transfer to the next flower. Research on crops including apples and tomatoes has found that wild bees, including solitary species, can contribute disproportionately to pollination relative to their numbers.
13. What is 'buzz pollination' and which plants depend on it?
Buzz pollination (or sonication) occurs when a bee vibrates its flight muscles at a specific frequency while gripping a flower, shaking loose pollen that would otherwise be locked inside the anthers. Bumblebees are particularly effective buzz pollinators. This technique is essential for plants including tomatoes, aubergines, peppers and some wild plants such as foxgloves and comfrey. Honeybees cannot perform buzz pollination. This is one reason why wild bees, including bumblebees, are ecologically irreplaceable even where managed honeybees are present.
14. How do I create a nesting habitat for solitary bees in a city garden?
Solitary bees have diverse nesting requirements depending on the species. The most useful things you can do are:
- Leave areas of bare or sparsely vegetated, well-drained soil for ground-nesting mining bees — these are the most numerous and most overlooked
- Install a bee hotel with tubes of varying diameters (3–10mm) made from hollow stems or drilled wood to suit different cavity-nesting species
- Allow old plant stems to stand over winter rather than cutting them back, as many bees nest inside pithy stems
- Position nesting structures in a sunny, south-facing spot sheltered from rain
Ensure diverse flowers are within foraging range, as a nest site without nearby food is of limited value
15. Do moths matter as pollinators?
Yes, significantly. Moths are among the most underappreciated pollinators. Night-flying moths pollinate plants that specifically evolved to attract them – flowers that are pale or white (visible at night), strongly scented after dark, and often tubular in shape to match moth tongue lengths. In the UK, species such as the elephant hawk-moth and silver Y moth are important nighttime pollinators. Many common garden plants – including evening primrose, white campion, honeysuckle and night-scented stock – are heavily or exclusively moth-pollinated. Supporting moths by including night-flowering plants and avoiding unnecessary outdoor lighting contributes to a complete pollinator community.
16. What is the role of wasps as pollinators?
Wasps are often overlooked as pollinators, but they do visit flowers for nectar – particularly open, flat-structured flowers such as umbellifers, ivy and some wildflowers. They are generally less effective pollinators than bees because they lack the specialised pollen-carrying hairs that bees possess, but they contribute to pollination across a range of species. Some specialist plants in other parts of the world are almost entirely wasp-pollinated. In the UK urban context, wasps also play an important ecological role as predators of pest insects, which benefits garden and green space health more broadly.
17. How does climate change affect urban pollinators?
Climate change affects pollinators in several interconnected ways. Warmer springs can cause pollinators to emerge earlier, but if flowers do not advance at the same rate, there may be a mismatch between pollinator activity and food availability. Hotter, drier summers may reduce nectar production in some plants. Milder winters can disrupt the overwintering of queen bumblebees, which need a sustained cold period to regulate their dormancy cycle. More frequent extreme weather events can damage habitats and reduce floral resources unpredictably. Urban environments may partially buffer some of these effects through the heat island effect and diverse plantings, but also risk amplifying them in heatwave conditions. Planting for resilience – diverse, native, year-round – is one of the best responses to climate uncertainty.
18. Can pollinators travel between rooftop gardens in cities?
There is good reason to think they can. In 2022, Pollinating London Together conducted a small pilot study across three rooftop sites in the City of London – at 80 Fenchurch Street, The Garden at 120, and Aldgate School – using a mark-and-recapture method to test whether pollinators move between elevated green spaces. Insects were briefly captured, marked with a tiny dot of non-toxic paint, and released. Pollinators originally marked at one rooftop site were subsequently observed at another, providing direct field evidence that movement between rooftop gardens does occur.
The study was limited in scale and conducted over a single day, so it is best understood as an encouraging proof of concept rather than a definitive finding. It does, however, support the idea that rooftop gardens can function as stepping stones in an urban pollinator network – not just at ground level, but vertically through the cityscape.
The study also suggested that building height may influence which pollinator species are present, with lower rooftops supporting a greater diversity of wild pollinators than higher ones. Again, this is a preliminary observation from a small pilot, but it points to useful questions for future research.
PLT continues to explore rooftop pollinator connectivity and would welcome partners interested in supporting larger-scale studies.