Saturday, January 12, 2013
The relationship between exotic and native flora and fauna in restoration projects within our cities.
An observation by Rex Bushell
Native flora restoration in cities is under constant pressure from hybrids, selections of genetic variations and selective breeding done by commercial nurseries targeting new and varied cultivars of native origin for the domestic urban market. These commercial variances will cross with many genetically pure species that may be planted by restoration groups or cross with old established canopy trees that have existed in the city for many years. Some species like flax, manuka, lancewood, kowhai and totara are particularly vulnerable.
Over time, depending on the life cycle of a particular flora species, this will create a genetic evolution within the native forest reserves in or close to, a city.
Is this good or bad? Either way it is inevitable. It can be slowed down by planting eco sourced plants but it cannot be stopped. For the flora purist this may not be something to look forward to.
To look at it from the native fauna angle, they will happily eat the berries or drink the nectar of a modified native. In fact, their participation is often the cause of genetic variation by transferring the pollen from a domestic selection to a native.
Because of the large variation of flora species within a city there is an opportunity to target non native plants that attract - as opposed to just feeding – a targeted fauna species such as the tui and bellbird. This is why Banksia integriflora is being promoted. There is plenty of opportunity to plant Banksia integriflora in parks around a city where exotic trees are planted and in domestic gardens without compromising the integrity of native restoration projects. The gardens of the University of Waikato would be an excellent example where natives and exotics are planted along side one another including Banksia integriflora resulting in a high population of tui.
Banksia integriflora may have a propensity to be invasive in some parts of New Zealand but this is not the case in the Waikato. Bunny and John Mortimer had a tree growing at their Taitua Arboretum and only ever got one seedling. Maxine Frazer has a QE11 block at Te Pahu and has a Banksia integriflora growing by her house and has never seen a seedling. On the road verge by 90 Wellington Street in Hamilton there is a very fine specimen that must be all of 100 years old with no proliferation of seedlings in the area.
To summarise, in city environments exotic flora tends to dominate over natives. Because of this management plans have to be more adaptable if our target is to reintroduce or sustain native fauna species within our cities.