Immigration’s a hot topic – and it applies to non-native plants, animals and insects, all over the world | Tim Blackburn

Humans have been moving species for thousands of years , but the rate at which aliens are arriving is speeding up.

For most of the last 500-odd years, a new alien species has appeared somewhere roughly every other month or so, or around seven new aliens per year worldwide.

The rate of arrival started to climb in the middle of the 18th century , as trade routes between the European colonial powers and their possessions were regularised.

It has continued to climb ever since by the end of the 20th century .

We have a moral duty to address the environmental problems we've caused, says Tim Blackburn .

Biosecurity regulations have reduced the rate of alien plant arrivals in New Zealand to almost zero .

Public awareness of threats helps the earlier a problem species is noticed, the easier it is to deal with.