Whanganui Midweek

Continuing the war against weeds

- Anne-Elise Smithson Anne-Elise Smithson is an environmen­talist from Auckland and Whanganui region enthusiast.

New Zealand has some of the strictest quarantine laws in the world. But as we pour effort into defending our border from invasive plants and animals, are we doing enough to get rid of those already here?

We are at war with weeds, and Parliament­ary Commission­er for the Environmen­t Simon Upton is calling for the Government to lift its game.

The environmen­tal watchdog’s newly released report Space invaders: A review of how New Zealand manages weeds that threaten native ecosystems is the first ever review of its kind in our country’s history.

The investigat­ion found that halting the “slow-motion botanical conquest” of our land has been hampered by inadequate leadership, limited informatio­n and haphazard and unco-ordinated actions. Legislatio­n on what introduced plants should be prioritise­d as targets for action, is absent.

You could say New Zealand is a poster child for the havoc brought on by weeds. Since early settlers first began transposin­g exotics from distant, temperate shores — mainly for horticultu­ral reasons — more than 25,000 exotics have made themselves at home in our temperate, South Pacific nation.

Each year about 20 of the existing introduced species “naturalise”, meaning they jump the fence and thrive in the wild without human help.

Some of those plants — many escapees from our farms or gardens — go on to spread and conquer. This adds to the already 1800 strong army

of weed species. For comparison, New Zealand has just 2300 native vascular plants.

Once an exotic plant starts spreading, it can be difficult to eradicate.

“It is a somewhat chilling fact that there is no record in New Zealand of any terrestria­l plant having been successful­ly eradicated when the extent of spread has been greater

than one hectare,” the commission­er’s report said.

We hold the dubious title of having an unusually large number of exotic plants. A recent study found the North Island and the South Island each had among the highest number of naturalise­d plant species of any island in the world.

Privet and woolly nightshade out compete native bush, vines like banana passionfru­it and climbing asparagus strangle understori­es, deceptivel­y beautiful lupins choke braided rivers, and gorse and wilding pines blanket large swathes of our countrysid­e.

The Horizons Regional Council Pest Management Plan details a list of nasties that threaten not only our forests, but our livestock and our livelihood­s.

Plants like field horsetail — well establishe­d in Whanganui and Rangitikei but limited elsewhere — is poisonous to livestock; African feather grass out competes pasture and Senegal tea blocks drainage channels, affecting both irrigation and waterway navigation.

The commission­er is calling for clearer direction from both the minister for biosecurit­y and the minister for conservati­on on managing weeds that have already made their way here.

Recommenda­tions include a publicly accessible national weed informatio­n database; a team to be set up by MPI and DoC to co-ordinate management with regional councils and nip new threats in the bud; and the developmen­t of a national policy direction on how weeds that grow in native ecosystems should be dealt with.

Critically, the report states that defeating weeds will not be achieved by top-down policies alone.

Most rural New Zealanders are already trying to undo more than a century’s work in excluding stock from gullies and restoring native vegetation — the very same community that has a crucial role to play in holding the line against this silent invasion.

Weeds may well be a poor cousin to other biosecurit­y threats, but if left to their own devices, they will transform our ecosystems beyond recognitio­n.

Time to turn back the green invasion.

 ?? Photo / Katikati Advertiser ?? Woolly nightshade out competes native bush. One of many introduced weeds threatenin­g our ecosystem.
Photo / Katikati Advertiser Woolly nightshade out competes native bush. One of many introduced weeds threatenin­g our ecosystem.

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