"Weeds can protect habitat"...
- observed @jon_sullivan in a recent Observation on Horseshoe Lake Reserve, Burwood, Christchurch.
Our experience in public reserves in the Kaipatiki area of North Shore Auckland leads us to agree wholeheartedly. It's one more reason to think carefully when planning intervention.
The most diverse habitat we've seen in the Birkdale/Glenfield neighbourhood was for decades used as an illegal dumping ground, with the most diverse remnant vegetation and natural regeneration hidden, protected from trampling and from most weeds by the rubbish and weeds on the outside.
Sadly, weeding the outer, visible margins of the area, along with construction of a walkway through the forest interior, made the public Reserve attractive and thus popular.
It became for a while a popular place to walk. Most people caused no damage, but cycling and jogging in winter rutted the path, making it boggy when wet, and then people began to walk on the revegetating path edges to avoid the mud.
The increased popularity of the site attracted Council budget allowing the felling of a mature pine on the roadside margin. The resulting loss of shade, without resources to monitor and weed that previously shaded streambank, allowed kikuyu invasion, followed by Japanese honeysuckle, ginger and Moth plant, inaccessible down a steep bank.
Freeing a large area of streamside from Pink Jasmine along the road edge allowed directly access into the bush from about 40m of roadside footpath. For reasons as yet unknown, little revegetation has occurred in this area in the 20 years since jasmine removal.
Hopefully we can learn to avoid the potential negative impacts of weeding by strategizing weed control, through thorough planning of pedestrian-only, low-impact, minimal-width sustainable paths, maintained by users adding dead ponga fronds and fallen wood that are usually within easy reach and break up easily.
Awareness of the damage caused by jogging and cycling on wet clay paths could be achieved through public education including pictorial signage, and the frequent presence of Site Curators/Kaitiaki/visitor guides in each natural heritage reserve.
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Our definition of weeds needs to be changed. They are indicators of deficiencies in the health of the soil.
Weeds are colonisers that are able to cope with poor, compacted and anaerobic soils. They function as 'roots in the ground' bringing to the surface nutrients and water from deep down, helping the growth of soil biology and protecting the surface from erosion.
In a natural progression they are replaced with other species as the soil improves: as organic material is added, and the microbiology in the soil increases. These changes cause the soil to gain structure allowing for water and oxygen to penetrate and allow the roots to deepen in the soil.
Managing this progression is a much better strategy than trying to remove weeds or to kill the them with chemicals that can also kill the biology in the soil, delaying the process of healing in the soil and the progression of species towards the end stage of mature forest.
I wholeheartedly agree about the change through progression, and have yet to see a weed-infested area "restored" through chemical use.
But how long till ivy, tree privet or Japanese honeysuckle die out through progression?
The progression often observed in North Shore Reserves and roadsides is
1.regenerating native forest with pest trees and shrubs scattered through it, recently including thousands of exotic palms, Phoenix the first to arrive about 20 years ago, and now joined by the other palms
2.Forest becomes mixed native/exotic
3.Weed vines spread from neighbouring properties and/or germinate on the sunlit margins, and gradually canopy the outer trees
4.Outer trees die and fall over, allowing more exotic trees and shrubs to germinate in the now sun-lit soil
5.The weed vines climb the next trees
6.Once trees have collapsed, kikuyu covers the vines
7.A larger area of kikuyu is mown
There is a credible theory by a Northland observer of this process that, without intervention, kikuyu will be the last plant standing in New Zealand.
Okay, the above is a hasty summary not covering all situations, but a progression observed to occur where there is no weed control.
Where there is rare chemical control without regular ie at least quarterly monitoring and follow up, the course appears to be the same but with more loss of native plants, and increasingly poor health of soil and trees, which, like us, have immune systems that are weakened by exposure to these chemicals.
I'm on a small farm near Kaukapakapa and know first-hand the truth of
what you just wrote. When we arrived on the farm Jasmine was so rampant
next to the house that we didn't even know until we started clearing it
that there was a wooden fence and a shed underneath. We have gradually
cut back the encroaching vines until some natives are in the clear but
there's a lot more to do.
Also, further out on the property, there were some stands of established
gorse. These I have cut down and mostly eradicated while the farm next
door, using spray to poison the gorse, has an ever-returning crop of
gorse everywhere.
On the other hand, there are seeds of natives dormant in the soil
waiting for the right conditions to germinate. Near where I grew up in
Mt Eden, there are still Totara trees springing up naturally in the
gardens, along with Cabbage Trees in profusion.
The work of Dr Elaine Ingham has proven that when the conditions in the
soil are naturally suitable for crops, even though there are weed seeds
in the soil they just don't germinate. When the soil conditions are
right for the weeds they flourish and the other plants don't.
Hard work removing troublesome species combined with proper management
of the soil seems to be a good combination.
Have you read any of the works of Allan Savory?
Not specifically, but as I have never used chemicals, I know first hand what happens naturally [edit: ie without chemicals, and with knowledgeable hand weeding] and enjoy the process immensely:) The trouble is, until there are people like us looking after every wild area, national and regional bodies charged with controlling the ever-hastening replacement of native species by exotic invasives will continue to resort to what they believe is the best solution, not having the budget to do what we do.
The result is that the only people with paid work in the field learn and practise only chemical "solutions", (and concentrations:) and have not the experience or the skills to trust in or practice the already long-known methods of non-destructive, species-comprehensive, site-based manual restoration. Only volunteers and private landowners have that luxury.
I only mention chemicals because I sympathise with the motives of the people who do use them. and because I cannot say for a fact it is always the wrong thing to do.
I do say, however, that where there is someone who knows how to control the weeds through a manual methodology and is committed to following it through for at least 3-5 years, chemical methods should be only considered after considering the alternatives.
The irony is, manual site-based restoration is such an enjoyable, fascinating and rewarding process,giving one a much more intimate experience of the site by being closely involved in the process of its restoration.
.....and now made even more thrilling by the process of iNat! At last, species IDs as needed, and other people's experiences to learn from...
Yea! How do we get people in high places to understand and appreciate the joy of helping the natural restorative processes in nature?
I do love being closer to nature here on our farm. Our general culture, however, is so far from nature and is too easily swayed by politics and advertising. It is an uphill battle to get the ideas of working with natural processes, rather than fighting against them, accepted.
I'll leave things there. Been good to share with you here, something I haven't done before.
I have a blog at https://pgtips91.wordpress.com/ with my lost post at https://pgtips91.wordpress.com/2018/03/
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