Heatwave and invasive plants – thrive or die!
It’s not a mirage – UK summers are getting hotter! If weather reports are accurate, the UK is about to experience its first heatwave of the year, and just like humans, some plants will love it and thrive, and some will quickly wilt. Which plants will survive depends on their genetic makeup, the environment they inhabit and their ability to adapt.
Invasive Non-native plants are set to increase by 36% over the next 3 decades and are more likely to survive the impact of a changing climate – in this article we explain why.
What happens to plants in a heatwave?
- Water depletion
If extreme heat continues for extended periods of time plant nutrients start to deplete as the ground dries up and plants start to die from water loss (desiccation) when more water evaporates from their leaves than is taken up by their roots.
The hotter the air the quicker the water molecules move – the faster water will leave the plant. This generally happens when air temperatures exceed 90 degrees F. And when the ground becomes barren of water there’s nothing to replace the rapid transpiration from the leaves.
- Plant stress
Plants tend to close their stomata (leaf pores) to conserve water and this restricts evaporation which aids cooling the plant – leading to plant stress. But drought-affected plants may open (rather than close) their stomata in response to excessive heat, exacerbating stress and making plant death more likely.
Equally warm, humid air with little or no air movement exacerbates the heat effect as the air becomes denser, slowing down evaporation. When this happens the plant’s leaves become saturated with moisture and open to attack from pathogens, leading to another type of plant stress.
- Nighttime fatigue
Plants perform different processes during night and day. During nighttime the plant will process and transport sugars to those parts of the plant that require energy the most. Sugar is important for plant growth and development. When nighttime temperatures are high (a common factor of heatwaves) this process is slower, resulting in restricted growth.
Survival of the fittest
Given the above factors that occur because of heatwaves, it’s clear that plant species best evolved, or able to adapt to heat extremes (both day and night) stand a greater chance of survival. Plants native to hot countries or heat induced environments (such as volcanic regions) will therefore be better evolved to deal with temperature extremes.
So where does that leave our native plants?
In short – they will need to quickly adapt to the changing climate and environment. Invasive plant control will need to step up a gear to ensure eradication programmes are effective, and equally adaptive.
The surprise factor
The recent Biodiversity Report (by IPBES) states that 6% of all alien (non-native) plants are invasive. They become invasive when they are introduced to a new environment and allowed to grow faster and more prolific than their native cohabitees. Once established their ability to spread and colonise large areas is what kills native plants.
We must also adapt
This ‘element of surprise’ that non-natives have becomes a winning factor in habitat dominance, which is a constant battle to counteract. Integrated Weed Management (IWM) is not a new concept – but it is becoming increasingly important as the weed control industry strives to offer more sustainable options that reduce herbicide usage and protect ecosystems.
What is IWM and why is it so effective?
IWM does not solely rely on one method of control, additional to herbicide often mechanical, biological or manual methods can prove incredibly effective. IWM is not a stand-alone product, it takes great skill and expertise to understand how to adopt the practice across a range of plant species.
There simply is no one-size-fits-all!
Knowing your species is the key. Knowing how a species may change it’s biological structure or growth pattern as a result of environmental factors such as heatwaves is even more important. We know that certain invasive species are already adapting to the hotter summers of the recent couple of years – we’re seeing spring growth in late winter (in the case of Japanese knotweed our surveyors spotted shoots before Christmas), and re-colonisation of aquatic plants such as Azolla further afield or downstream than ever before due to riverbank erosion in dry spells. Himalayan balsam is growing more rapidly than ever – hot, dry and windy weather casting its exploding seed heads to a wider parameter.
Be vigilant
If we want to avoid a native species wipe-out situation we have to be more aware of infestations, and they may crop up in unexpected places.
- We need businesses to watch out for reduced water quality in rivers or reservoirs due to invasive aquatic weeds
- Homeowners and commercial land owners should watch for colonies of highly invasive plants such as Field horsetail which can affect residential properties as well as managed land.
- Anyone out walking or working outdoors should be extra careful around Giant hogweed or Hemlock as these are poisonous and harmful to humans and pets.
If you have any concerns about a suspected invasive plant get in touch.