Council record on Western Springs Forest planting is poor

The Society is concerned about the Council’s promises of replanting a Forest based on its recent past performance in the area when removing pine trees. 

It is more than 5 years since pine trees were removed by the Western Springs Stadium Wall by the Bullock track. When you visit this walking track area you can see replanting has taken place yet the area is covered in weeds: kikuyu, gorse and wattle weed. It is nowhere near the level of beautiful native bush understory that we already have in the Western Springs Forest, which be destroyed if the pine trees are removed. 

The Council seem to have given up on weed management here and is relying on community group efforts (Forest & Bird volunteers have spent several weekends there trying to reduce the level of weed infestation). If this is the level of maintenance that we can expect for Western Springs Forest, it is likely to become a weed wonderland for decades until native regeneration closes the canopy, just as it has done already in the bush that is there now.

And this is despite the fact that it is an area that should have been easy to replant – it has good access, had all of the pine logs removed rather than left on the ground, and had very little weed cover to begin with.

A wonderland of gorse, kikuyu, wattle weed and a wilding pine fight it out for supremacy with the cabbage trees and manuka by the Bullock Track Stadium wall

The planting they have done seems to be for a landscaped garden rather than to replace native bush. Why do they keep planning cabbage trees which are a swamp tree on a hillside?  The existing understorey of the WSF is rich and diverse and suited to its environment. It is not possible to destroy a naturally regenerated forest and then replant it like a native tree garden and say it will be the same Forest. 

Then we go to the pine trees that were removed from the alongside the fence on the Zoo side of the forest, over 13 years ago. On the Forest side of the fence the ground is almost impassable, strewn with felled trunks and high fire risk ‘eco-piles’ of smashed branches.

A bonfire-ready ‘eco pile’ of pine slash (with bonus razor wire left behind by the contractors)

Mile-a-minute and woolly nightshade are doing exceptionally well in these areas now that the pine canopy is gone and they have plenty of light. The extensive ground cover provided by the large number of simultaneously felled trunks is no barrier to weed species but does make their control much more difficult to carry out and makes replanting almost impossible. Mile-a-minute is on the nationwide biosecurity watch list as it smothers and kills most plants from ground level to medium canopy and prevents the establishment of native plant seedlings.

Mile-a-minute and woolly nightshade fill the gaps in between pine corpses

On the Zoo side of the fence there has been some native planting, but it is mostly a wasteland of kikuyu, with thriving clumps of bamboo and gorse. Hardly the “special urban native bush experience” the council touts as its vision for the Western Springs Forest (“Pine stand to go native“, 2018, ourauckland.aucklandcouncil.govt.nz/articles/news/2018/4/western-springs-pines/ )

Some of the ‘special urban native bush experience’ at Auckland Zoo after council replanting efforts 13 years ago

These two case studies – over 5 years ago and then 13 years ago show why the Society is so concerned for the pristine transitioning native understorey that remains. The community is being promised a  “special urban native bush experience in Western Springs” but the photos show the opposite will happen. Our already special urban native forest will be destroyed and if we look at the past experiences of Auckland Council on this site, we will be left with weeds and no native forest. Or it could all just slide down the de-stabilised slope and into the creek.

Large trees provide exponentially larger environmental benefits

In 2017 Auckland Council’s Research and Evaluation Unit published a report on the state of Auckland’s urban forests, in the Monitoring Research Quarterly newsletter.

They said that “Large trees provide exponentially larger environmental benefits – such as carbon storage, area shaded by canopy and building cooling effect – compared to small trees of the same species; a typical 20m tall street tree may provide three to seven times the benefit of a 10m tall one, and these benefits continue to rise rapidly above 20m.”

and also that “Only about seven per cent of Auckland’s urban forest canopy
is greater than 20m in height”
.

If you look at their map (from 2013), you see that the Western Springs Forest is the only 30+ forest in the whole of the Waitemata Local Board, with only scattered trees of similar heights in the Auckland Domain or in the shattered forest fragment to the east of the Western Springs stadium. That fragment alongside the Bullock Track has since then already been clear-felled and is now a struggling, weed-infested patch of regenerating scrub – a far cry from the lush, diverse area of native bush that exists under the Western Springs Forest’s pines.

Figure 9: Urban forest cover within the suburban zone of Waitematā Local Board showing the maximum height of urban forest patches (in metres)

Even in the 20-30m category the board region only has Western Springs park, the Domain, Cox’s Bay and Western Park as providing any significant contribution.

“The majority of trees greater than 20m are concentrated in a small number of public parks, including The Domain, the Western Springs area including the steep escarpment below Old Mill Road, Western Springs Park and the zoo, Cox’s Bay Reserve, small pockets within Ayr Reserve, and Western Park (Figures 9 and 11). There are also scattered examples taller trees in some smaller parks, including Alberon Reserve, Scarborough Reserve and Dove Myer-Robinson Park (Parnell) and Point Erin Park.”

The Council’s own analysis states that “International research has shown that many of the benefits attributed to urban forest are disproportionally provided by larger trees.”

“This is particularly true for environmental-ecosystems benefits such as providing shade, sequestering carbon, trapping pollutants and reducing water run-off. It seems intuitively correct that larger trees will cast more shade, have higher wood volume, greater total leaf area to trap pollutants and higher water requirements, and this is backed up by experimental evidence.”

“This data suggests it is critical to retain the larger trees”

And yet they plan to cut down the entire, and only major, stand of 20+m trees we have.

View or download the newsletter here: http://knowledgeauckland.org.nz/assets/publications/MRQ-08August-2017.pdf

The article is largely based on data from this report from 2013: http://knowledgeauckland.org.nz/assets/publications/TR2017-006-Urban-forest-of-Waitemata-Local-Board-in-2013.pdf