An Emerging Ecology

Sir Paul Callaghan shortly before his death extolled the goal of a pest-free New Zealand that would enable the native fauna, notably native birds to prosper once more. The pests he was considering were animal pests; possums, mustelids, feral cats, rats, mice, wasps etc. that either prey on our native birds, eat their eggs or compete for food resources. However there is an equally great challenge paralleling the loss of native birds over much of the country that will also impact upon their long-term survival and the restoration of indigenous values. It is change to our landscapes and ecosystems via subdivision, clearance, land use by man and natural changes that are occurring as plant species introduced by humans following European settlement spread and establish their own mixed adventive ecosystems and successions. The latter usually overwhelm the indigenous and transform the landscape character.

In the Wakatipu basin fires were used initially to clear native beech forest, but totara once grew on the lower slopes of the Remarkables above the Kawarau River. I have observed over the sixty plus years of my life, the tussock-covered hills give way to sycamore, rowan, ash and larch forests. The river margins all the while are flanked by crack willow. The sycamore, rowan and other species, with pronounced autumn colour, are now giving way to exotic conifer-dominant forests: notably Pinus nigra (Austrian pine), Pseudotsuga menziesii (Douglas fir), and sometimes Pinus radiata, Pinus ponderosa or other pine species, with Larix sp continuing. On the lower Crown Range hill north-east of Arrowtown, Pinus wallichiana (syn. Pinus griffithii), Himalayan pine is well-established. Chamaecyparis lawsoniana, (Lawsons cypress) is spreading at the northern fringe of Queenstown.

At present the forests of these exotic species are localised, mostly spreading from the towns or homesteads where they were first planted. Being spread by wind mostly, some by birds and having had time to establish large populations and perhaps over time having developed strains more suited to local conditions, the spread of seedlings into native ecosystems (e.g. remaining tussock areas) seems to be accelerating. Perhaps changes to the local climate including more rain are aiding this. I noted stray Douglas fir seedlings emerging in the tussock grasslands near the top of the Cardrona Road this summer and similar spread on Coronet Peak. No one seems to be culling these pioneer arrivals which in time will seed and further spread, altering our ecosystems, habitats and landscapes. Over time the seed bank of native species local to the area is likely to be lost for ever, an undervalued taonga.  

At the Roaring Meg Power station beside the Kawarau River a small group of Douglas firs planted for amenity in the 1940s or 1950s had spread alarmingly by the 2000s. All but those near the power station were sprayed about 2012. Now, along with a grey dead forest clothing the hillside there is a flush of Douglas fir seedlings emerging. More and complete action is needed. Meanwhile, nearby, an old world species, Clematis vitalba, old man’s beard or traveller’s joy, has established and is entering the Wakatipu with a few plants now present at Arrowtown. In the future this species may invade the lake side areas where a beautiful form of Clematis paniculata (pauwhananga) currently thrives.

Pandora’s box has truly been opened and the challenges are large–scale. Our country has great border control today but what has already been allowed in poses huge problems.

What can be done?

Many years ago in the days of the local Arrowtown Borough Council, a land owner would receive a letter from the Council’s noxious weeds officer advising of the requirement to remove noxious weeds from a property including from the road frontage. No such role now occurs. Hemlock, once controlled, is rife today and the range of species that might be considered as environmentally damaging or noxious has widened considerably. The problem is compounded where historic scheduled pioneer trees are also of species now known to be invasive. E.g. the Mary Cotter sycamore tree in Arrowtown’s main avenue.

A group has been formed to tackle the “wilding pines” challenge in the Wakatipu.

With regards to the larger emerging picture, I suggest the following:

• Survey and assess the nature and extent of the problem. This should be carried out by appropriate experts, the project driven by the local Council. Botanists, ecologists and horticulturalists should lead the project. The project should be publicised and opened for public submissions: Other passionate interested parties might have advice, ideas and contributions to make. Problem species distribution should be mapped using GIS technology and species should be listed and added to an environmentally damaging species inventory to be recorded as an Appendix to the Local District Plan. Non-problem species should be identified also, with both lists periodically reviewed as time passes and circumstances change.
• Education:
  oHave a Council re-vegetation manual that maps the local natural ecosystems and lists
      for each local ecosystems the plants natural to each, as originally occurring in the
      area. This would assist in informing native re-vegetation projects and be of use to
      landscape architects, nurserymen and others.
  o   Desirably the New Zealand primary syllabus would include studying the local natural
       ecology and adventive ecology and include identification of plant species in both
       categories.
  o   Control methods should be advised: Removing weed species and invasive species
       prior to their seeding should be stressed. The local Council should produce leaflets on
       weed species and their control including recently observed new species to the area
      likely to cause a problem if ignored now.
• Ensuring that nurseries do not sell plants of species known to be environmentally damaging in the area or in New Zealand as a whole. Nurseries’ stock should be inspected annually in this regard.
• Have a range of reserves that preserve indigenous habitats.
• Having more leadership and funding from the top: Preserving our ecosystems and landscapes needs to be valued and prioritised by Government and local Council’s and funded appropriately.

Accepting the likely permanence of an exotic vegetation element in the area, those exotic species found in the area that are not (currently) environmentally damaging/invasive should be recorded also. This list might inform nurseries, land owners and landscape architects in regards to suitable plant choice. Curiously, large old Picea sitchensis, sitka spruce, planted in early days have never seeded in the area and might be considered for further use.

Landscape architects should support the cause, should acquaint themselves with the native species original to the area, use local native species as far as possible in their planting schemes to maintain habitat and indigenous landscape values, and should avoid the use of exotic plant species known to cause problems.