RESEARCH, INNOVATION AND ENTREPRENEURSHIP AT THE UNIVERSITY OF WAIKATO
3
The benefits of
bringing nature
back to cities
AN INTERNATIONAL team of researchers has been
studying green spaces in 110 of the world’s cities and while
some cities support surprisingly high numbers of plant
and bird species, cities everywhere have lost significant
biodiversity through urbanisation, and New Zealand does
not come out well.
Professor Bruce Clarkson, Dean at the Faculty of
Science & Engineering at the University of Waikato is
part of the international team that first met three years
ago in Santa Barbara in the US, at the National Centre
for Ecological Analysis and Synthesis. Since then they
have assembled the largest global database of urban plants
and examined the patterns and associations of urban
plant diversity.
“At Waikato, we’d already gathered a lot of data
about New Zealand’s urban ecological restoration, or
lack of it,” says Professor Clarkson. “The government has
supported research in this area since 2005, so we knew that
New Zealand cities had much higher proportions of
naturalised introduced birds and plants than many other
countries. We were the most isolated in the study but the
most ‘invaded’ by introduced plants.
“Our colonial settlers wanted to replicate the mother
country, so planted exotic species and did not understand
the consequences that introducing stoats, weasels and rats
would have on native birds.”
The international study has worked with huge data
sets. The researchers found that, on average, cities retained
about 8% of bird species and 25% of plant species when
compared to similar areas of undeveloped land. But it’s not
all doom and gloom, says Professor Clarkson.
“We found that cities support surprisingly high
numbers of plant and bird species, but cities have also lost
significant biodiversity with urbanisation.” Hamilton is
one such city.
“There’s been systematic removal of habitat in
Hamilton, it’s down to about 1%. The largest native
forest remnant in the city’s 10,500 hectares is Claudeland’s
Bush covering just 5.2 hectares. New Plymouth is
doing well with just over 8% but Perth in Australia
still retains about a quarter of its indigenous habitat.”
The research also showed that the more urban land cover,
the lower the density of bird species.
Professor Clarkson says that because New Zealand
cities have much higher proportions of naturalised
introduced birds and plants than elsewhere in the
world, enhancement of existing natural areas, weed and
pest control and reconstruction of new indigenous-
dominated habitat is very important. “It’s vital we
include remnant vegetation and restore natural areas
in the design of cities,” he says.
“I think policy makers need to be thinking hard
about the value of regional and global biodiversity
conservation. The reasons for green spaces are many.
They provide refuge for native species and migrating
birds, and if we create and conserve more green
spaces, then we’ll be able to support even more bird
and plant species. It makes good sense, and a positive
side-effect is the community involvement that’s
generated by working for a common goal.”
Many cities world wide are making a “balanced
nature diet” part of their long-term planning, involving
residents in some projects.
It’s not easy being green
»
»
Air filtration
– tests have shown that
plants and other greenery can reduce
nitrogen dioxide levels.
»
»
Cooling
– trees and other vegetation
cool the air around them through
shading and evapotranspiration.
»
»
Co-use corridors
– greenbelts and
bluebelts allow wildlife to disperse
between larger habitats.
»
»
Community cohesion
– civic pride may
facilitate neighbourhood greening and
vice versa.
»
»
Carbon storage
– urban trees can store
and sequester carbon.
»
»
Biodiversity
– more species reduces
single species dominance.
»
»
Food for all
– community gardening for
food production.
Source – Conservation this week
(University ofWashington)
Managing the spread of mangroves
IN NEW ZEALAND the spread of
mangroves
is
concerning
some
communities, especially those people
living around harbours and estuaries, but
these tropical plants have their uses as they
trap and cycle organic materials, chemical
elements and nutrients in the coastal
ecosystem. They also stabilise the coastline,
by reducing erosion from storm surges,
currents, waves and tides.
Two scientists from the University
of Waikato, Drs Karin Bryan and Julia
Mullarney, have been awarded funding from
the US Office of Naval Research (ONR) to
carry out a mangrove study on the Song Hau
River in Vietnam where the Mekong Delta
meets the sea. The ONR says tide-dominated
deltas perhaps hold the most promise for
advancing basic understanding of delta
dynamics and for relevance to existing and
future Navy missions.
Dr Mullarney has already travelled to
the site and will be returning “to the mud”
several more times to collect data about
the vegetation structures and how they
influence hydrodynamics in the area,
and how that in turn feeds back into the
sedimentary system.
The ONR has carried out pilot studies
in the region, and is now carrying out a
more extended study that includes the
scientists from New Zealand, Dr Mullarney’s
former colleague from Washington State
University Dr Stephen Henderson, other
researchers from the US, the Netherlands
and Vietnam.
“We use acoustic Doppler profilers
that send out sonar waves and tell us
how fast the current is moving,” says
Dr Mullarney from the Department of
Earth and Ocean Sciences at Waikato.
The university recently purchased a high
resolution sonar instrument, a vectrino
profiler, and Dr Mullarney says having
that piece of equipment at their disposal
helped to make preliminary measurements
in New Zealand to shape the proposal
they put to ONR.
Dr Bryan doesn’t get to live on a river
boat and wade among the mangroves
OCEAN STUDY: Drs Karin Bryan, left, and Julia Mullarney with a Nortek Aquadopp Profiler
that measures the variation in ocean currents with depth.
in shorts and t-shirt. Her job back
in Hamilton is to develop a model
that will enable scientists to predict and
examine issues around the plants, such as
what would happen in channels, to banks
and floodplains if the trees were removed.
“This research may have benefits for
New Zealand,” says Dr Bryan. “We don’t
GREEN SPACES:
Restoring natural
areas has multiple
benefits for cities.
yet know if mangroves cause sedimentation,
or if sedimentation allows mangroves to
expand. We do know that these plants have
a big blue carbon stock [carbon captured
by living coastaland marine organisms]
– they are significant globally, but are
expanding alarmingly in New Zealand.”
PROFESSOR BRUCE CLARKSON
