Restoring our surrounds

I went to a very interesting Wellington Botanical Society talk last night, by Paul Blaschke of Friends of Owhiro Stream. Paul was talking about their work revegetating the catchment of the Owhiro Stream in southern Wellington.

It stimulated an intriguing discussion about how and what we should be restoring, which in turn relates to what our goals for conserving biodiversity are.

Ecological restoration is a vexed issue, with many controversial aspects, so it was good to discuss, learn, debate, and think.

For instance, some people believe that only plants present in an area before humans arrived should be used in restoration.

Collections of plant specimens, like that held by Te Papa, can play an important role in establishing where plants are/were distributed.

Houpara, coastal five-finger, Pseudopanax lessonii, is native to the northern North Island, but not to Wellington. However, after being introduced by people, it now grows wild in Wellington (and many other parts of New Zealand outside its native range [http://blog.tepapa.govt.nz/2009/06/10/our-promiscuous-pseudopanax-plants/]). There are now a reasonable number of New Zealand plants occurring wild outside their indigenous distributions, entirely as a result of human activities. Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Houpara, coastal five-finger, Pseudopanax lessonii, is native to the northern North Island, but not to Wellington. However, after being introduced by people, it now grows wild in Wellington (and many other parts of New Zealand outside its native range). There are now a significant number of New Zealand plants occurring wild outside their indigenous distributions, entirely as a result of human activities. Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Other people go even further when considering restoration, saying that only locally-derived material should be used.

 Photo by Leon Perrie. (c) Leon Perrie, Wellington.

Mahoe, Melicytus ramiflorus, occurs indigenously throughout most of New Zealand. For restorations in, say, Wellington, should only material derived from local-Wellington sources be used? Or, is it okay to use mahoe plants from anywhere? Photo by Leon Perrie. (c) Leon Perrie, Wellington.

But, is it practically possible to ensure such ‘eco-sourcing’? Do the costs outweigh the benefits?

And, what geographic scale is appropriate for eco-sourcing? Should plants be from the same province, river-catchment, …, or hillside?

Is it already too late, at least for some species/communities/regions, to even attempt to ensure that pre-human patterns are preserved? Has the colloquial horse already bolted? Are the ‘genes’ out of the bottle?

And, on a temporal scale, what are the implications from past and future climate-change? Many lowland New Zealand plants were more widespread during past warmer periods (and, similarly, much restricted when it was colder). Indeed, many warmth-loving plants were eliminated completely from New Zealand during the Ice-Age. Given the dynamism of biodiversity, what are appropriate parameters for restoration targets?

Managing ‘nature’ is often a tricky business…

2 Responses

  1. Colin Ryder

    I chair a restoration group that is currently drafting a management plan for a block of native bush, part of which we own and part of which we co-manage with neighbours. Two respected amateur botanists on our Board have argued against any planting of any native species, even eco-sourced ones, and we should allow nature to take its course, with the only interventions being pest control and weeding. They have cited you as the authority advocating such an approach. I would welcome your comments on this issue.

    Reply
    • Leon Perrie

      Hi Colin,
      I’m fine with planting eco-sourced native species (or non-weedy exotic species!). That’s often needed to protect the structural/ecological integrity of an area of vegetation.
      But I am cautious about attempts to hurry along succession. For example, in a patch of (intact) regenerating scrub, why plant seedlings of forest dominants (e.g., podocarps)? If they’re close by, they’ll probably introduce themselves (not necessarily immediately, but within the long time scales that succession processes operate on). If they’re not close enough to introduce themselves, it is arguably dubious whether eco-sourced material can actually be obtained. There are grey areas (e.g., an absence of birds may mean natural dispersal can’t occur), but I’m generally in favour of letting nature heal itself – it has a remarkable capacity to do so (once pests and weeds are controlled).
      Kind regards,
      Leon

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