Re-planting New Zealand

In regard to Bob Brockie’s recent article in the Dominion Post (24 June 2013, page A8), here is some rationale for viewpoints about plants that some commentators have teasingly called “eco-fascism”. Instead, they are logical expressions about the conservation of New Zealand’s biota and ecosystems, including their genetic integrity.

For any effort claiming to be about ecosystem restoration, it is my opinion that local material of locally-native species should be used.  We know that most New Zealand (plant) species naturally occurred in only part of New Zealand.  We also know that local populations can have their own genetic characteristics.

This means that a given region of New Zealand has a set of native (plant) species, present at the time of human arrival, with each species having its own set of regionally-native genetic variation.  If protecting this native variation is not a goal of ‘restoration’ efforts, then such efforts are not actually restoration but gardening.  Gardening is fun and can have conservation benefits, but it shouldn’t be misrepresented as restoration.  And some gardening, even if well intentioned, can have negative conservation impacts.

Juvenile and adult plants of fierce lancewood, Pseudopanax ferox.  This is one of many native New Zealand species that occur naturally in only part(s) of the country.  It is also a species with marked genetic differences amongst groups of its populations.  Photo Leon Perrie. (c) Te Papa.

Juvenile and adult plants of fierce lancewood, Pseudopanax ferox. This is one of many native New Zealand species that occur naturally in only part(s) of the country. It is also a species with marked genetic differences amongst groups of its populations. Photo Leon Perrie. (c) Te Papa.

Example of genetic variation within a species: blog post on fierce lancewood, Pseudopanax ferox.

Links to maps of three Polystichum shield ferns occurring in different parts of New Zealand: Polystichum oculatum, Polystichum wawranum, Polystichum cystostegia.

There’s still plenty of room for exotic species.  I have just planted my own garden with a wealth of New Zealand species not native to Wellington, as well as with Australian species.  I’ve done this because I like them, aesthetically; simple as that.  But I’ve picked well-behaved species or, at least, species not known to spread aggressively.

It is surely ecologically irresponsible to plant exotic species known to cause problems in susceptible areas.  Would you plant old man’s beard next to a forest remnant or contorta pine next to upland grassland/shrubland?  I hope not, because they are demonstrably problematic.  So why plant karo or (northern) houhere in Wellington?  They are not native to Wellington (but to the northern North Island), and are known to spread aggressively, displacing locally-native species.

Karo (Pittosporum crassifolium), which is native to the northern North Island, smothering the locally-native Melicytus obovatus at Titahi Bay, Wellington.  Photo Leon Perrie. © Te Papa.

Karo (Pittosporum crassifolium), which is native to the northern North Island, smothering the locally-native Melicytus obovatus at Titahi Bay, Wellington. Photo Leon Perrie. © Te Papa.

If you want a specific outcome, pick a well-behaved species.  Brockie mentions feeding birds, and (exotic) gums and bottlebrushes are good for this, but don’t use coast banksia (Banksia integrifolia) which is already known to be an aggressive weed in New Zealand.

Personally, I like the majestic size of the (exotic) pines, macrocarpa, and gums of Wellington’s townbelt.  These species are all reasonably well-behaved, but some more so than others.  There are a few pine seedlings here and there, but all I have looked at have the three-needled clusters of Pinus radiata rather than the two-needled clusters of Pinus muricata.  It seems that the latter could be used, at least in Wellington, to create a stand of ecologically-‘safe’ ornamental pines.

Brockie listed several New Zealand species not native to Wellington: pohutukawa, puriri, kauri, and rengarenga.  I can’t see how they could justifiably be used in any Wellington effort claiming to be a “restoration” – they weren’t in Wellington at the time humans arrived.  Kauri and rengarenga are well-behaved in gardens.  Reports of ‘weedy’ (self-sown) puriri are slowly increasing, so it is worth keeping an eye on in case it does become a problematic weed.  Pohutukawa regenerates abundantly around urban Wellington, with its small seeds spreading everywhere.  I remove any seedlings that establish in my property before their roots can damage paths and walls.  But pohutukawa is barely established in Wellington’s ‘wild’ areas; nevertheless, it has become a weed in several other countries, so it should be monitored here. 

Karaka was also mentioned.  It is an interesting (and challenging) case.  Karaka was cultivated by Māori, and some planted groves are still evident.  Many botanists believe that karaka was brought to the southern North Island and South Island from the northern North Island by Māori, but others think it was present in the south before humans arrived.  Either way, it appears that karaka is spreading to sites where it did not occur previously, and it has the potential to fundamentally change the character of such sites.

An abundance of karaka seedlings, under an adult that has established in regenerating native forest. Naenae, Wellington.  Photo Leon Perrie. © Leon Perrie.

An abundance of karaka seedlings, under an adult that has established in regenerating native forest. Naenae, Wellington. Photo Leon Perrie. © Leon Perrie.

Te Papa blog post on some of the native plants cultivated by Māori, including karaka.

We should be clear that New Zealand native species are not always ‘good’; certainly not when introduced overseas, and sometimes not even so within New Zealand. 

Te Papa blog post on native New Zealand plants causing trouble overseas.

Context is of course important in determining values.  Gorse is abhorred by many farmers for smothering farmland, but it makes a wonderful nursery for regenerating native forest.

I think it is great that we debate conservation values, so Brockie’s article is welcomed.  We need to be clear as a nation and as communities about what our goals are for conservation.  Perhaps we decide we cannot afford to use locally-native material, but let’s debate it first.  We do have a lot of urgent biodiversity issues in New Zealand, but wholesale restoration of our forests is not one of them, so there is no need to rush.  Furthermore, given a chance (principally space and time), New Zealand’s forests are great at restoring themselves; they have done it at the end of each glacial period.

I fear that some of the activities currently being done in the name of conservation will be viewed in 50 years time with the same contempt (and perhaps without the frustrated understanding) that we now view the purposeful introductions of exotic plants and animals that cause us problems.  For a country so concerned about genetic engineering, I’m amazed how blasé we are about undertaking enormous re-engineering of our ecosystems.

12 Responses

  1. Leon Perrie

    Hi Julie,
    It’s great that you’re interested in the issue. Some of the species used by your landscaper might pose a problem for nearby ecologically-sensitive areas like Whitireia Park. However, rest-assured that your garden is a small drop in the bucket, so please don’t feel devastated. Perhaps a course of action is to keep the karaka and pohutukawa etc. in the short-to-medium term as shelter for your other plants, with a view to removing the karaka and pohutukawa etc. before they start flowering and seeding prolifically. Rather than immediately pulling plants out of your garden, a more direct way to help Whitireia Park might be to join the Friends group (http://www.gw.govt.nz/whitireia-park-restoration-group-formerly-known-as-the-onehunga-bay-restoration-group/) and help them weed plants they consider undesirable.
    All the best, Leon

    Reply
    • Julie

      Thanks Leon, I appreciated your reply. The karaka trees are gone, but the other things – pohutakawa, houpara, akeake, and pittosporum cultivars have all stayed, and we’ve tried to add in a few things native to the area. Like you said, it’s a drop in the bucket ; )

  2. Julie

    Hi there, I am a new homeowner in Titahi Bay and recently worked with a local landscaper to do some ‘gardening’ (not restoration! but we did mention eco-sourcing and using species that were originally in this area, as well as exotics). Our back yard is mostly grass with pohutakawa, karo, ngaio, and exotic abelia hedging as well as ivy. In the end we paid $2,000 for many of the ‘natives’ that are not native to Welllington, including 10 karaka trees, 6 pohutuakawa seedlings, and the purplish pseudopanax varieties mentioned here, as well as cabbage trees and various forms of pittosporum. I am now devastated that we spent so much money on plants which are regarded as ecologically out of place – and even potentially damaging to places like Whitireia Park. I too wish this info had been more widely disseminated. I did find the Wellington Conservancy guide eventually, but did not know ahead of time which plants the landscaper would choose. What to do now with all these expensive undesirables?

    Reply
  3. Karen

    Kia ora Leon, an interesting blog. I’m no botanist, but as a keen gardener it would never occur to me to select ‘well-behaved’ natives (or exotics) to help preserve regionally-native genetic variation. (I do know to steer clear of ‘old man’s beard ‘ and wild ginger. But that’s about the extent of it).

    To Andrew’s point, how do school kids and us non-botanists learn this stuff? When you say that we need to be clear what our goals are for conservation, how ARE our most urgent biodiversity issues identified and agreed? How are they then disseminated with a view towards increasing general knowledge and informing critical debate in this area?

    Finally, how does Bob Brokie know that his Dom Post article has prompted your response and an interesting conversation amongst seven of us, not to mention helping to increase the knowledge base of at least one of us? Am sure he’d be pleased to know that we’re paying attention!

    Reply
    • Leon Perrie

      Hi Karen,

      There’s some information already available. Greater Wellington regional council have a useful booklet available from this page: http://www.gw.govt.nz/native-plant-guide/

      But it is complex, with some 2500 native vascular plant species, occurring in different parts of the country. To my knowledge, there are not accessible lists of which species are native to a particular region. But the Plant Conservation Network (http://www.nzpcn.org.nz/) includes information on where each native species naturally occurs in New Zealand.

      It should also be possible to produce regional lists for, say, the 100 New Zealand species that are most commonly planted, and indicate whether they are native to each region. If they are, people who care might seek eco-sourced material from their local plant nurseries so as to protect the genetic integrity of the locally-native populations.

      We could also have lists of the native species to avoid because of their weedy tendencies. Fortunately, these lists, if they focused on the most troublesome species, would be quite short. For Wellington, it might be something like: Pittosporum crassifolium (karo), Pittosporum ralphii (karo), Pseudopanax lessonii (coastal five finger) and its hybrids with lancewood, Hoheria populnea (houhere), and perhaps(?) Metrosideros excelsa (pohutukawa) and Corynocarpus laevigatus (karaka). These species are of course fine within their native regions/habitats, while other species would be added in other regions; for instance, Brachyglottis repanda (rangiora) is a problem in Otago.

      Everything else (i.e., about 2400 species) might be safely ‘ignored’ in that they are unlikely to be planted and are not known to be troublesome.

      Providing regionally-focused lists might be a suitable challenge for the many botanical societies we have in NZ. To be really useful, such lists/guides would have to be supported by informative pictures, allowing everyone to distinguish the plants they have at hand.

      That would be a start to helping the interested public deal with this issue.

      In the context of having time to think carefully about how we might replant forests, I’d say that our urgent biodiversity issues involve preventing extinctions and protecting (and restoring the functioning of) the remnant native ecosystems that we still have. But, I’d welcome other opinions. I’m not sure how we agree as a nation, or how ideas are best disseminated. Ideas seem to bubble along in the conservation/environmental community, and some become sufficiently mainstream to affect central and local government, and then community, practices. Ecosourcing and locally-native are concepts already embraced by some land managers but certainly not all. The idea of ecosourcing has been around for at least 20 years.

      For me, my personal views and values mean that I try professionally to encourage people to consider these issues. But I am conscious that local kaitiakitanga may be simply too hard/costly. If that is what the community chooses, so be it, but I hope it as actually a choice rather than we lose the integrity of our local plant/animal communities and genetic diversity without most people realising it.

  4. Leon Perrie

    Thanks Mick, Ant, Peter, Andrew, and Helen for your interest and comments.

    It is important we (1) document what is happening, and (2) debate what we want.

    Getting data and making it available provides the information for the debate. Build the evidence so communities and land managers in particular are not able to ignore the issue but have to make a decision about whether to take action, and be responsible for the consequences.

    Helen, Peter – the website NatureWatch (http://naturewatch.org.nz/) provides a great way to put observations into the public record (where, as they accumulate, become less easy to ignore). You can even include notes about the apparent impacts etc. of the plants. See http://naturewatch.org.nz/observations/356786 for a good example (although this is a record about the threatened species rather than the threatening species).

    Alternatively/additionally, if you have permission to collect, I welcome the donation to Te Papa’s permanent collection of dried plants of specimens of plants found growing wild outside their native distribution. My email is leon.perrie@tepapa.govt.nz

    Andrew – yes, I think you’re right about “plant blindness”. What do you, and anyone else, think should be the key messages we try to disseminate? Resources indicating the native distribution of species are becoming increasingly available (see Te Papa’s species maps, the New Zealand Virtual Herbarium, the New Zealand Plant Conservation Network, Naturewatch NZ, the New Zealand e-Flora), although they are far from perfect. That knowledge is actually quite complex (e.g., each area has its own set of native species), but perhaps the use of that knowledge can be distilled into simple principles.

    Reply
  5. Helen Chambers

    Pohutakawa is just starting to colonise the shoreline of the Waitakere River mouth at Cjharleston on the West coast .They are also growing on Tree ferns. This will completely change the character of the area. It is only in the past six years that the seedlings have survived the winter. They are now flowering. DoC are not interested-or have no funds.

    Reply
    • Robyn Smith

      I have the same problem at Whitireia Park in Porirua. They colonise open areas and are going to change the natural native escarpments. We also have a problem with Pseudopanax hybrids and karaka slowly spreading throughout the bush remnant. Karo is smothering the Cook Strait endemic Melicytus aff obovatus and Hebe elliptica on the cliffs north of Titahi Bay. Problems everywhere.

  6. Andrew

    A public debate does require some knowledge of our native species. My experience teaching primary / secondary children is that few have an adequate knowledge about NZ species. Maybe another case of “Plant Blindness”, see: http://artplantaetoday.com/2011/01/28/eradicating-plant-blindness-in-the-21st-century/

    Reply
  7. Peter Russell

    Well said Leon, although I have to say that pohutukawa IS becoming well established in Wellington’s wild coastal areas. It clearly has the potential to colonise and dominate most/all exposed coastal rocky areas. Now would be the best time to halt its spread by drawing a line and preventing it spreading further (seedlings generally seem to emerge within 100m of parent plants).

    Reply
  8. Mick Parsons

    Kia ora Leon
    Another great article.
    Banksia: If planted out of the sand country it does not seem to be a problem. I think soil temperature is critical for germination (sandy soils may reach critical level). The other aspect of karo (maybe a good one) is that as a seres it may not be that long lived ( 40 yo trees look near the end of their lives) and other natives may have a chance where it has established. Regional councils are pushing it as a riparian plant on dairy farms assuming this to be the case. I am not so sure and, as you suggest, there needs to be a lot more widespread discussion on this; not easy when most of our land resource users barely know a native from an exotic. Because of the exploitative mindset of land users they are always after a ‘quick fix’ when it comes to shelter. The mistakes of the past are likely to be repeated if your concerns do not generate more widespread discussion.

    Reply
    • Antony Kusabs

      Leon. Great post. Good distinction made between restoration and gardening. Very important when trying to restore plant communities with ecological integrity.

      Mick. Interesting comments around Banksia and farm plantings. Regarding karo longevity, unfortunately 40 years is still long enough to shade out low stature plant communities, on the coast for example. Councils have plenty of fast growing natives to choose from other than karo: Coprosma, Pittosporum, Sophora, Cordyline.

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