UNLESS…Earth-friendly Chroniclers: Challenge 9 ~ Invasive Plants

Caring for our environment is a great concern for many and Jane at www.justanothernatureenthusiast.org is hosting a blog challenge every Friday on topics of an ecological or environmental nature.  It’s a good way to raise awareness and ‘check the pulse’ on what’s happening in different parts of the world on common issues which affect us globally.  This week’s subject is Invasive Plants.

Alien vegetation clearing is a hot subject here in the Cape Peninsula. Recognition of invasive species and their negative impact on the indigenous, and endemic fynbos was recognised as far back as 1938 when three Australian Hakea species were declared noxious weeds.  Alien clearing in the Cape Point reserve started in the 1960’s as well as Table Mountain and the Silvermine nature reserves.  Finally in the 1990’s sufficient funds were allocated to do the job properly and rid the entire Peninsula’s natural areas of the scourge of invasive plants.

Working for Water since it’s inception in 1995 and now run by the Department of Environment has created jobs and poverty alleviation through their programme of environmental conservation initiatives, such as the clearing of invasive alien vegetation.  In Cape Town a further, unique public/private partnership was created: The Ukuvuka (meaning “Wake-up” in Xhosa) Operation Firestop campaign which aimed to rid the Peninsula of alien invasive plants after the devastating wildfires in 2000.

Complete eradication is easier said than done!  It’s a process that has to be assiduously followed, as we can see here in our neck of the woods where clearing was undertaken near Miller’s Point in 2012 but where there was no follow up and some species have rebounded with renewed vigour.  The City used a private contractor but their work was disappointing in that they took out historic old trees (gums) which are not deemed an invasive species, as well as many of the indigenous shrubs Soon after the clearing the fynbos plants appeared, but now three years later and the invasive exotics like Port Jackson (Rooikrans) Black Wattle, and pines are all flourishing.

*Abstract from “Impacts of inasive alien plants on water quality with particular emphasis on South Africa”

“We review the current state of knowledge of quantified impacts of invasive alien plants on water quality, with a focus on South Africa. In South Africa, over 200 introduced plant species are regarded as invasive. Many of these species are particularly prominent in riparian ecosystems and their spread results in native species loss, increased biomass and fire intensity
and consequent erosion, as well as decreased river flows. Research on the impact of invasive alien plants on water resources has historically focused on water quantity. However, although invasive alien plants also affect the quality of water, this aspect has not been well documented. Alien invasive plants increase evaporation rates, and reduce stream flow and dilution
capacity. The biomass inputs of alien invasive plants, especially nitrogen fixers such as Acacia spp., alter nutrient cycles and can elevate nutrient concentrations in groundwater. Alien plant invasions alter the fire regimes in invaded areas by changing the size, distribution and plant chemistry of the biomass. More intense fires increase soil erosion and thereby decrease
water quality. In contrast to riparian invasions, aquatic invasive plants have been more extensively studied in South Africa and their impacts on water quality have been relatively well monitored. Water quality in South Africa is rapidly deteriorating, and all factors that influence this deterioration need to be taken into account when formulating actions to address the problem. The changes in water quality brought about by alien plant invasions can exacerbate the already serious water quality problems.”

*J Chamier, K Schachtschneider, DC le Maitre, PJ Ashton, BW van Wilgen

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17 thoughts on “UNLESS…Earth-friendly Chroniclers: Challenge 9 ~ Invasive Plants

  1. Liz, it is interesting that invasive concerns date back as far as 1938 on the Cape Peninsula. I’m curious when invasive plants started to be a concern here in the States, that is something I could look into.

    It’s encouraging to learn that your Department of Environment is working to properly clear and replant and, at the same time, create jobs and poverty alleviation through their programme of environmental conservation initiatives. That sounds like a good model – potentially a win/win situation for the environment, resource preservation, and economy.

    Sad that even with the best goals in place, errors occur. From your photos, it looks like the Gum trees were very well-established. Are they being replanted?

    Do I understand that Port Jackson (Rooikrans) Black Wattle, and pines are the native plants? If so- great to hear they are flourishing! Is the eucalyptus an invasive? Clearing those stands looks like a major impact.

    Your quote from the impact abstract mirrors what the facilitators at the workshop I attended recently were saying about some of the devastating impacts non-native “plant bullies” can have on watersheds and biodiversity of ecosystems.

    We are all connected in this problem… thank you for giving a window for us to see how invasive plants affect your area of South Africa.
    ~Jane

    1. Jane, one of the reasons and driving force behind the alien clearing projects is that Table Mountain and it’s flora, the Cape Floral Kingdom are recognised as a Unesco World Heritage site. That’s good news as we’re losing species at a rapid rate. Another crucial aspect is the consequence of the terrible fires that the Cape experience, and the detrimental effect that alien vegetation (highly combustible) has. While fire is a natural part in plant regeneration, the high temperatures of aliens isn’t. The eucalypts, blue gums, which aren’t native are bad from that aspect, as well as being water hungry. Oops, I see that I forgot to list the ten most noxious/ invasive species, I pressed that Publish button too soon! I wasn’t very clear with my labelling in identifying the bullies from the Fynbos – apologies for that. The worst culprits are the Port Jackson (Rooikrans), Black wattle, Hakea, Pines. The results from the clearing programme in the Miller’s Point area were disappointing as there was no follow up, and the aliens are back in force. If I may, can I come back with a second post?

      1. Thank you, Liz… of course, please come back! I think this challenge is best left open-ended. That’s the thought behind the name change to Chroniclers. Does that make sense?

        Oh, with this comment, I can appreciate how much more devastating the replanting mistakes are. I recall the fear in your posts when the fires were raging. Sadly, I suspect fires will be more menacing as more of us face drier climate conditions plus the invasive problems…

        “Fynbos” that is a new vocabulary word for me- a distinctive type of vegetation found only on the southern tip of Africa. It includes a wide range of plant species, particularly small heatherlike trees and shrubs.

      2. Hi Jane, have been gathering up more photos to add to this very topical subject. Next post coming up soon. We’re pretty lucky at having the diversity we have here with our fynbos species… and in it forming one of the six plant kingdoms. Liz.

  2. I didn’t realise the impact of invasive plants on water. Here we have some invasives, Himalayan Balsam is the one that I see most often. It grows on river banks, up to 8 foot high and chokes out our native species, I think they are losing the battle to control it.

    1. I liked the way Jane referred to invasive plants as ‘Bullies’ but the Himalayan Balsam sounds to be way beyond that. Wonder if there is a list of the world’s most destructive invasive species….. Going off to consult Mr Google.

  3. We have similar issues in my local area of South Australia, great effort has gone into removing feral Olives but 3 or 4 years later you wouldn’t know the work had been done. Kikuyu has been a blessing and a curse here too because of its toughness.

    1. Some species are just too successful! Those that reproduce multiples of seeds … Lay dormant in the soil, and then voilà spring up in abundance. Know what you mean about the Kikuyu – it hangs in there through dry summers and drought, but gets everywhere when the rains come?

  4. We have a similar problem on a much smaller (thankfully) scale here Liz. We have a wonderful Conservancy on which I’m proud to serve and an excellent program in place to champion eradication. Our biggest issue is the Tallow Tree, which robs our native plants of the nutrients they need to flourish. Unfortunately it is the only plant, other than sweetgrass, that gives us color in the fall, turning a gorgeous red. SO, neighbors are very resistant to its removal. Be we continue to educate and provide assistance with removal and treatment so progress is being made. Great job highlighting the issue.

    1. Makes it difficult when the exotics are showy, keep up the good work though, Tina! The results of running a conservancy must be pleasing when you see the results of thriving ecosystems. I’m off to google Tallow trees…

  5. Great post — and so interesting to connect it to water issues too.

    We have a lot of Eucalyptus trees here in California too, and in fact, the abundance of these trees helped fuel a devastating firestorm in the East Bay hills in the 1990s. The firestorm swept through over 1,500 acres (6.2 km²), destroyed almost 3,000 family homes and over 400 apartment and condominium units, with an economic loss estimated at $1.5 billion. Although the wind conditions during the fires were abnormally strong, the trees, and specifically the oils generated by the trees were also blamed for the intensity of the fires. Sadly, 25 people died and 150 were injured.

    1. Hi Lola Jane, I remember seeing the news reports way back in the 1990’s on those terrible fires and the devastating results in California. It’s interesting though that ‘aliens’ such as Eucalyptus became a part of the settler landscape. Fast growing and useful, but at least we know now of their detrimental impact. Jane has opened up some interesting topics on her UNLESS … Challenge. It’s enlightening to read comments from different continents on similar issues. 🙂

      1. Yes indeed, Jane’s UNLESS…Challenge is great for nature lovers, and for the opportunity that it gives us all to exchange information, and learn from one another 🙂

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