RHS John MacLeod Annual Lecture

Gardens are hotspots of biodiversity in an urban environment. “Gardens and allotments support by far the highest abundance of bees and other pollinators in cities,” says Mark. “They are by far the most important habitat when you look at the proportion of area they make up.”

Research by Dr Nick Tew during a PhD with the RHS also found that residential gardens provide an estimated 85% of the nectar available to pollinators in UK cities – and that non-native plants are a key source.
 

“Allotments have a high pollinator abundance but a small total area in cities, so they contribute little overall, but may have potential to expand,” says Mark. “Gardens occupy a large area and support lots of pollinators, but could perhaps be even better. Parks also cover a large area but have fewer pollinators, so have huge potential for improvement.

“We shouldn’t forget that urban gardens have many wider benefits too, both for people through wellbeing, and for the environment by providing carbon storage, cooling, absorbing rainfall to reduce flooding, and more.”

“Gardens aren’t in isolation,” says Mark. “They are part of a landscape at neighbourhood and city scales. Biodiversity is mobile and operates at a landscape scale. This means we need to manage gardens at a landscape scale, which requires understanding and planning, and also an understanding of the social factors around decision-making and how neighbours influence each other.”

“Individual actions do scale up to impact biodiversity, but gardens also need to be managed as a network of patches rather than individual units.”

• We know small changes to garden management can make a difference, but more experimental studies are needed
• Understanding the social drivers behind gardening attitudes and behaviour are key to harnessing gardens for conservation
• Retain existing gardens and increase plot sizes in new developments; collaborate with developers to increase biodiversity
• Incentivise householders using policy tools, e.g. regulation and financial incentives
• Certification schemes and community initiatives

About the speaker

Dr Mark Goddard is an urban ecologist working on biodiversity conservation and the provision of ecosystem services in cities where most of us live and work.

A focus of Mark’s research has been understanding the biodiversity of private gardens – in particular, the ecological and social factors that influence garden biodiversity in multiple scales. 

The John MacLeod Annual Lecture was created to highlight important and inspiring topics on horticultural science. A broad audience of RHS members, scientists, policymakers and the media is invited every year to hear luminaries of the scientific field give talks on major research projects or new areas of thought.

The lecture’s namesake, Professor John MacLeod, who died in 2010, was a plant scientist and Professor of Horticulture at the RHS. He was also chairperson of the RHS Scientific Committee and was a powerful advocate for horticultural science. He was acutely aware of its pressing relevance in sustaining the natural environment and world food supplies.