An international team of researchers, including a scientists from the UK’s Centre for Ecology and Hydrology (CEH) has warned that the rise of invasive species around the world shows no signs of slowing down. In line with predictions for climate change, the number of species shifting range to new areas is on the increase.

CEH ecologist Professor Helen Roy, and her colleagues on the international team, believe globalisation could also be fuelling an unprecedented increase in invasive species. The researchers looked at data kept on non-native species around the world, including records kept by the British government. Using records from these databases around the world, the ream created a single worldwide database with information on 16,000 species.

Having developed the single database, the scientists established that more than a third (37%) of all recorded invasive species were introduced to new areas since 1970. In fact, a record 585 new species were recorded in a single year - 2004. This includes the Harlequin ladybird, which has been a focus of study for Professor Roy, and the Asian hornet, which sparked a surveillance operation when a nest was discovered in Gloucestershire last year.

Professor Helen Roy said, "The rapid escalation in species arriving in new regions of the world has been concerning ecologists for many years. One example is the Harlequin ladybird which is threatening other species within the invaded range.

"People from across the UK have themselves become actively involved in helping to report and record species such as the Harlequin ladybird through citizen science initiatives such as the UK Ladybird Survey. This is proving hugely valuable in helping us to understand the ecology of invasive non-native species.

"It is really important that we work together both through global research collaborations, as demonstrated by the international team contributing to this study, but also across society with people taking part in surveillance on the ground for new arrivals such as the Asian hornet."

Lead author Dr Hanno Seebens, from the Senckenberg Biodiversity and Climate Research Centre in Germany, added, "For all groups of organisms on all continents, the number of alien species has increased continuously during the last 200 years. For most groups, even the rate of introduction is highest recently. Barring mammals and fishes, there are no signs of a slow-down and we have to expect more new invasions in the near future.

"We also observed a distinct increase in first record rates of vascular plants in the 19th century, probably as a result of the intensification of horticulture. The rates of new introductions of other organisms, such as algae, molluscs or insects, increased steeply after 1950. This is most likely a consequence of the ongoing globalisation of trade."

The researchers acknowledged that the ‘unprecedented’ increase in alien species could produce a richness of species regionally, these shifts in species’ spread can have consequences for native ecosystems. Local species could become extinct, and there could be a homogenising effect on plants and animals as a result.

Commenting on the potential role of agriculture in the movements of invasive species, Dr Seebens told Farming Online, “It is known that horticulture is an important (probably the most important) pathway for plant invasion. Many of the alien plants we see now established in nature were introduced for ornamental purposes and planted in botanical gardens, parks or private gardens. Many of the plants we can buy in garden centers are non-native and it is comparatively easy for the plant to escape from a garden.”

The Senckenberg scientist said that it’s less easy to provide concrete figures to illustrate the role an intensification of horticulture has played in this pattern, but pointed to a rise in alien species in the 19th Century, which could well be linked to ‘plant hunters’, who brought thousands of new plant species to Europe for ornamental purposes. Dr Seebens added, “Another important aspect seems to be the introduction by European settlers into colonies around the world or the release/plantation of species by so-called acclimatisation societies, which attempted to satisfy the demands of European settlers.”Dr Seebens is currently researching the role climate change is playing in these shifts, and said, “Climate change clearly leads to shifts in species ranges and in some cases may have benefited the invasion, but it may also be that in other cases new invasions have been prevented because of these range shifts.”

The doctor said that, based on current understanding, the effects of climate change are likely being overwhelmed by the roles trade and horticulture have played in introducing invasive species.