Invasive Non-Native Species Part 1

Understanding biological control in the fight against Invasives.

Courtney Brain

This month we will be celebrating Invasive Species Week (15th - 21st May)!

To raise awareness of the harm invasive species are having on our native ecosystems, we will be releasing a three part blog series - so you can learn all about the steps we are taking to keep invasive species under control.  

Controlling invasive non native species is a difficult task, which is why successful control or eradication often takes years to achieve. Without any natural control mechanisms in their new introduced environments these species are able to dominate their new environments...unless we intervene.

The main two control mechanisms adopted to reduce the presence of invasive plant species have been chemical and manual control.  

Chemical control involves the use of herbicides to kill young and mature plants before they can produce viable seeds. This is not only expensive, requiring permits and qualified personnel, but the use of such chemicals can be restricted or banned in particularly sensitive habitats as they can be damaging to surrounding environments and species.

Manual control refers to the physical removal of these invasive plants by individuals or groups of people, this option can be very labour intensive and costly, particularly on large scales.
Until relatively recently these two options have been the only options available to those struggling against invasive plant species. But thankfully, there is now a third option – biological control.

Biological control refers to the use of living organisms, such as insects or pathogens, to control invasive or pest populations. By re-introducing a natural enemy, that would help to control the invasive in its native range, the invasive species becomes limited and is less capable of dominating these new introduced environments.

This control mechanisms aims to control and manage these invasive species by utilising natural enemies which provide equilibrium and balance rather than achieving eradication.
These natural enemies are selected based on years of research, not only discovering the species in the native range but also years of lab-based research to determine how effectively this pest species can manage the invasive. There is lots of testing of the possible biological control agent on native species, to ensure there is no harm on the native species or ecosystem.

Most of these biological control agents are monospecific meaning they can only consume and survive on a single species – the target invasive. This modern research based method for developing biological control agents is much more regulated by international regulations and procedures.

There are several key benefits to using this form of control over manual and chemical removal methods:
- Reduced environmental impact as no chemicals are required which would have adverse impacts on ecosystems, reducing the over reliance of herbicides for weed control .

- Reduced long term costs as fewer applications of treatment are required, compared to long term chemical control required to achieve similar or less significant results .

- Sustainable control option as the weeds will continue to be attacked by these natural enemies capable of establishing populations .

- Capable of spreading to other nearby populations of the target invasive just as they would in their native range (unless stopped by physical, environmental or chemical barriers) .

- Restore ecosystem balance by reducing the density of these invasives allowing native species to recover and recolonise regions where they were previously out-competed by the invasives.

Like all methods of control, there are also a few disadvantages associated with biological control:

- Designed to control the invasive rather than eradicate the species on which it depends .

- Significant start up costs of developing these control species, including extensive research and quarantine periods which could take years .

- Further costs associated with other control mechanisms, if required simultaneously .

- Long timescales to achieve control, some species can take 5 to 10 years to establish populations capable of controlling the invasive.

But overall, considering the impacts of other control options, biological control is definitely the way forward!

Our Test and Itchen Invasive Non-Native Species project seeks to utilise biological control where possible, but more on that in the next blog post...