Goats control weeds at forest restoration project

2 May 2007

Goats control weeds at forest restoration project in Island Bay

Several goats were released at a forest restoration project in Island Bay this week to help control environmental weeds. Goats are a serious threat to native forest because they are voracious eaters of woody native plants. However, several goats are being treated as temporary guests at the Manawa Karioi Ecological Restoration Project to help address a challenging weed problem. The goats are all neutered males and are contained by a deer fence in a c.1.5ha area dominated by introduced plants such as gorse.

The Manawa Karioi Society manages the ecological restoration project which occupies c.12ha of Tapu Te Ranga Marae and is the vision of Kaumatua Bruce Stewart. "One of our main tasks is controlling numerous species of environmental weeds, most of which are garden escapes" said Peter Russell, ecologist and Chair of the Society. "Our biggest challenge is dealing with large infestations of Japanese honeysuckle and old man's beard in our main gully.

We tried controlling the weeds with hand tools for a few years, but that proved to be futile. It was also impossible to deal with masses of severed weed material without leaving vines in contact with the ground where they could potentially take root. Vigorous regrowth of blackberry meant controlling regrowth of the target weeds was very difficult too.

Spraying herbicides wasn't an option for many reasons. The gully is so steep and the weeds so dense that herbicides would have had to be applied repeatedly by helicopter. The likely costs, non-target impacts and risk of spray-drift onto adjacent properties ruled this out. After much contemplation we came up with the idea of using goats.

First we researched the use of goats for weed control and consulted several ecologists and goat farmers. Although we did not identify similar situations in which goats had been used to control environmental weeds, what we found out was very encouraging. Goats are commonly used to control agricultural weeds such as gorse on marginal farmland, usually with reasonable success. In the past the biggest problems seem to have been caused by inadequate fencing, resulting in escapes and insufficient grazing pressure on weeds.

It was immediately obvious that if we used goats we would need secure fencing. We certainly did not want to detract from Wellington City Council's attempts to control goats on the Wellington Peninsula. The goats, vegetation, water supply and fence are checked regularly to minimise the chances of any problems arising. We are grateful to several neighbours who also keep a close eye on things.

After just a few months the impact on the weeds was very encouraging. The main targets, along with less problematic weeds such as pohuehue, climbing dock and holly-leaved Senecio, have been eaten back even more than expected. There has been no evidence of goats attempting to escape. The small amount of native vegetation in the fenced area has suffered minimal damage so far because the goats seem to prefer eating blackberry. As the amount of weeds is reduced we will be able to continue protecting selected native plants with wire mesh and 44 gallon drums.

With the additional goats released this week we now have a total of ten. All are young, neutered males which are relatively docile and unlikely to attempt to escape. We will ensure there is enough food, shelter and fresh water in the enclosure so they have no incentive to seek "greener pastures". However, in the unlikely event that any goats escape and are not recaptured they will be unable to breed. We consider that the minimal risks associated with this project are outweighed by the certainty that, unless controlled, the weeds at Manawa Karioi will continue to grow and spread elsewhere.

As well as wanting to reestablish native forest at this site, we feel we have a responsibility to prevent weeds spreading from it to other areas. However, Japanese honeysuckle, old man's beard and many other weeds already occur on nearby land. We are pleased that Wellington City Council has promised to control them on adjacent Council land. We hope local residents will feel compelled to do likewise and are happy to provide them with free identification and advice.

A major aspect of this project is clarifying the extent to which goats can be used to control environmental weeds, in particular Japanese honeysuckle and old man's beard. We are taking photographs regularly from several fixed points which will enable qualitative comparisons to be made. We will ensure that the results of this experiment and all that we learn from it are available to anyone interested in minimising herbicide use or using goats to help control environmental weeds. It was partly on this basis that funding for the project was provided by the Environment and Hertiage Fund of the Lottery Grants Board and WWF.

So far the results are very promising. Goats may not completely eliminate the target weeds, but we are confident they will digest the bulk of them and make the area accessible so we can remove any remaining weeds and plant more natives. We expect to be able to remove goats from the site within two or three years.

Our website www.mk.org.nz has further information: Home; Resources; Weeds

ENDS

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