Allotment Associations & Horticultural Groups in Harrow, Middlesex


Biodiversity in Harrow, Greater London and beyond


The London Invasive Species Initiative (LISI): londonisi.org.uk

Invasive Non-Native Species (INNS) are one of the largest threats to global biodiversity after habitat loss and destruction. They cost the British economy an estimated 1.7 billion annually. The London Invasive Species Initiative (LISI) has been created to help address these environmental and economic problems within the Greater London area.

Are all non-native species a problem? The majority of non-native species do not cause any problems. Very few of them have a negative impact on our economy, health or environment but it is crucial to identify which non-natives have potential to become invasive so they can be managed appropriately.

What is an invasive non-native species? An invasive non-native species is any non-native species that causes, or is thought may cause, serious negative impact on our native species, our health or our economy. The distinction between non-native and invasive is important as there are many non-native species that are not invasive and pose no threat.

So why do species become invasive? Plants, animals, fungi and micro-organisms have become increasingly mobile throughout the world. This has brought species into ecosystems that have developed without them, and without the conditions that limit their growth in their natural system (nutrients, moisture, pests, diseases, etc.). This allows some species to grow and reproduce unchecked. The ecosystem is unable to cope with this new species and is thrown off balance. This population increase can then result in damage to the ecosystem, our health or our economy and more often a combination of all of these.


LISI Species of Concern Chart

What's the Problem? Invasive non-native species affect our ecosystems, lifestyles and livelihoods in a range of different ways. In brief,they can:

• out-compete native species
• create pressure on native species through direct predation
• negatively affect human health
• increase flood risk
• create navigation hazards within canals and waterways
• affect horticulture and agriculture
• introduce and spread diseases to native species

The following links will take you to images of the major invaders:

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