Pavement gardens are crucial to urban biodiversity
They are often little more than a square metre of plants, yet pavement gardens are a source of life. PhD candidate Joeri Morpurgo conducted research in the centre of Amsterdam and The Hague and discovered how important small green spaces are, especially for cities.
With his colleague Margot Huurdeman, environmental scientist Morpurgo studied 65 pavement gardens for traces of life. They looked at 50 such gardens in the Weesperbuurt neighbourhood in Amsterdam (south of the Hortus botanicus) and 15 in the Zeeheldenkwartier neighbourhood in The Hague − that neighbourhood has way fewer such gardens, he explains.
Old school identification
‘It actually was a really simple study. We sat there with a field guide. You measure the size of the plants and what kinds of flowers there are. And then it was 15 minutes of catching insects with bottles and nets. It’s really very old school but that’s how we went about it.’
They found 235 plant and 154 insect species in around 100 square metres of pavement garden. ‘That’s a gigantic number of species, more even than is usually found in natural areas’, says Morpurgo. The pavement gardens are often hot and dry in the summer and these are the perfect conditions for exotic plant species such as hollyhocks. ‘Whether we want these exotics is debatable but they are good for urban insect diversity at any rate.’
‘There is a bit of a honeybee surplus in the city because everyone in Amsterdam has a beehive nowadays’
Alongside the ‘indestructible’ hollyhock weevil, the researchers found lots of hoverflies (good for aphid control as larvae and for pollination as adults) and a huge number of honeybees. ‘There is a bit of a honeybee surplus in the city because everyone in Amsterdam has a beehive nowadays’, Morpurgo smiles. What are not doing so well are butterflies, only two of which were seen fluttering past the pavement gardens.
The importance of insects is often linked to our food production. They pollinate crops that we can go on to harvest and eat. There is much less food production in cities but a great diversity of insects is important there nonetheless, says Morpurgo.
Extra genetic reserve
‘You then have an extra genetic reserve in the city if things go wrong with insect populations in agriculture. We also think it is important to have birds, fish and other animals in cities. Insects serve as food in many instances. So birds and fish ensure mosquitos are not too much of a nuisance for city dwellers.’
The more flowers the better
So a city’s small green spaces are of great ecological value. Still deliberating about a mini garden in front of your house or on your balcony? ‘Out with the tiles and in with the planters! Choose plants you like. It’s fine if that means exotics from the garden centre. The more flowers, the better for pollinating insects. And if weeds aren’t getting in the way of your lovely plants, leave them be. They also attract lots of insects.’
Morpurgo has also started a garden on his fourth-floor balcony. ‘I’ve got centipedes and woodlice there and I really didn’t introduce them myself. But they get there anyway.’
Text: Tim Senden
Main photo: Flickr.com / RdA Suisse