Our Changing World for 11 February 2021
Audio, Radio New Zealand
Liquefaction lessons from the 2011 Christchurch earthquake, and biotechnologists doing interesting things with plants.
Liquefaction lessons from the 2011 Christchurch earthquake, and biotechnologists doing interesting things with plants.
A city’s planted trees, the great majority of which are in private gardens, play a fundamental role in shaping a city’s wild ecology, ecosystem functioning, and ecosystem services. However, studying tree diversity across a city’s many thousands of separate private gardens is logistically challenging. After the disastrous 2010–2011 earthquakes in Christchurch, New Zealand, over 7,000 homes were abandoned and a botanical survey of these gardens was contracted by the Government’s Canterbury Earthquake Recovery Authority (CERA) prior to buildings being demolished. This unprecedented access to private gardens across the 443.9 hectares ‘Residential Red Zone’ area of eastern Christchurch is a unique opportunity to explore the composition of trees in private gardens across a large area of a New Zealand city. We analysed these survey data to describe the effects of housing age, socio-economics, human population density, and general soil quality, on tree abundance, species richness, and the proportion of indigenous and exotic species. We found that while most of the tree species were exotic, about half of the individual trees were local native species. There is an increasing realisation of the native tree species values among Christchurch citizens and gardens in more recent areas of housing had a higher proportion of smaller/younger native trees. However, the same sites had proportionately more exotic trees, by species and individuals, amongst their larger planted trees than older areas of housing. The majority of the species, and individuals, of the larger (≥10 cm DBH) trees planted in gardens still tend to be exotic species. In newer suburbs, gardens in wealthy areas had more native trees than gardens from poorer areas, while in older suburbs, poorer areas had more native big trees than wealthy areas. In combination, these describe, in detail unparalleled for at least in New Zealand, how the tree infrastructure of the city varies in space and time. This lays the groundwork for better understanding of how wildlife distribution and abundance, wild plant regeneration, and ecosystem services, are affected by the city’s trees.
Urban forager and food writer, Liv Sisson finds all sorts of tasty treats in the Otautahi city centre.With some of the housing and buildings destroyed in the earthquakes, a rewilding has taken place providing a range of edible plants. Liv Sisson gathers produce thriving on berms and near the Avon River.
Motoko Kakubayashi joins us from Toyko where they are also about to mark a significant anniversary. A few weeks after the 2011 Christchurch earthquake, a magnitude 9.0 earthquake hit the east coast of Japan, triggering a tsunami that destroyed large parts of the coast, including damage to the Fukushima Dai-ichi Nuclear Power Plant. More than 15,000 lives were lost, more than 2000 still remain missing. In one afternoon, half a million people became homeless, and the search for family and friends at evacuation shelters began.