Christchurch study finds larger, more diverse gardens support more pollinators

What is the background?

Rapid urbanisation reduces the diverse flowers and nesting sites that bees and other pollinators need, while roads, buildings, and foot traffic disrupt their movement between food sources. Urban pollinator habitat New Zealand research looks at whether city green space can offset some of that loss.

What happened?

A University of Canterbury PhD candidate studied pollinators at 14 community gardens across Christchurch, examining how garden size, plant diversity, and the surrounding landscape affect which bees and flies visit and remain. The research found that larger gardens with a greater diversity of flowering plants supported richer and more abundant pollinator populations than smaller, less diverse plots.

The study came alongside a separate discovery: researchers confirmed a native Australian bee species, absent from official Christchurch records for 65 years, had reappeared and established populations across the city.

How did it happen?

New Zealand’s native bees don’t live in hives — they nest in the ground, often in sunny, bare patches of soil, which makes them easy to overlook or accidentally destroy through paving or heavy garden mulching. Understanding this nesting behaviour, alongside foraging needs, lets garden and park planners design spaces that actually support native pollinators rather than only ornamental honeybee-friendly planting.

The bee rediscovery came from routine population surveys rather than a targeted search, underlining — as the researcher who identified it noted — how much remains unknown about pollinator populations even in well-studied urban areas.

Why does it matter?

Pollinators support both food production and wider ecosystem health, and their decline is a documented global trend. Evidence that city gardens — spaces already present in most urban areas — can meaningfully support pollinator populations gives councils and community groups a low-cost intervention: prioritise garden size and plant diversity in existing green space, rather than requiring new dedicated reserves.

A 65-year absence-then-rediscovery also demonstrates that urban wildlife loss isn’t always permanent extinction — populations can persist undetected or re-establish where suitable habitat exists, which is a genuinely hopeful finding for conservation planning.

What were the key results?

• Pollinators studied at 14 community gardens across Christchurch
• Garden size and plant diversity found to directly affect bee and fly abundance
• Larger, more diverse gardens supported richer pollinator populations
• Native Australian bee species (Leioproctus launcestonensis) rediscovered in Christchurch after 65 years
• Rediscovery found through routine population surveys, not a targeted search
• Native NZ bees nest in bare soil patches rather than hives, informing habitat design
• Findings add to national research mapping floral resources for pollinators

What happens next?

University of Canterbury researchers plan to continue surveying Christchurch gardens to track pollinator population trends over time.

Council landscaping teams are expected to weigh garden size and plant diversity more heavily in future green space planning.

Researchers said they will investigate how widely the rediscovered bee species has spread beyond the initially surveyed sites.

National pollinator mapping research is expected to incorporate the Christchurch findings into future urban planning guidance.