The spread of non-native species across the globe is a major concern – species out of their natural range can cause millions of pounds of damage, spread diseases to humans and livestock and threaten native wildlife. They are a huge financial burden to control, but almost impossible to eradicate. New invasive species reach foreign lands by hitching a ride on our trade routes, so changes to global trade could have serious implications for our economies and our ecosystems.

Invasive species – species that become so successful when introduced outside their native range that they begin to cause harm – are a serious concern for ecologists because they disrupt ecosystems, leading to loss of biodiversity and ultimately, the natural services we rely on so heavily. The main route by which species are introduced to new lands is international trade – increasing global trade means the risk of introducing new invasive species is very high.

Invasive species aren’t just a concern for ecologists – they have major economic implications, too. In the USA, invasive exotic species, such as fire ants and zebra mussels, are estimated to cost $120 billion each year in crop damage and livestock losses, damage to wild habitats, and control and eradication costs. Although there are an estimated 50,000 non-native species living in the USA, only about 4,300 are classified as invasive. Invasive species are the primary risk facing 42% of all species currently listed as threatened or endangered.

Non-native species represent a breakdown of the natural regional distinctiveness of the planet’s plants and animals, with major consequences for biodiversity, human health and wellbeing, food security and the economy. These human-mediated changes to ecosystems globally are in most cases irreversible – it’s easy enough to introduce a couple of rats to an island, but eradicating them again has proved extremely difficult. In fact, movement of species is one of the key characteristics scientists are now using to define the present, human-dominated geological epoch – the anthropocene. Humans have been moving plant and animal species around for millenia. Widespread movement of species began as early as the 1500s, when global exploration and colonialism were born, brining huge changes in trade, agriculture and industry, and re-shaping human demography. But it wasn’t until the 1800s that the rate of alien species introductions started to soar in Europe and North America with the birth of the Industrial Revolution, which increased international trade and expanded the transport networks with canals, roads and railways. As trade boomed, so did the explosion in alien invasive species.

One study in 2001 found that non-native (alien) plants are most common in Europe and North African countries with a high and lots of imports. Transport networks were an important component, as we the percentage of land designated as a protected area. This study highlighted the importance of trade in carrying non-native species around the world.

Currently, several major multinational trade deals are under negotiation, which could haves serious implications for the movement of invasive species. For instance, the Trans-Pacific Partnership Agreement (TPPA), is a trade agreement between twelve Pacific Rim , which aims to increase trade by lowering trade barriers (e.g. tariffs) and establishing an . The final proposal was signed in February this year in New Zealand, after seven years of negotiations, and it now awaits ratification before it’s rules come into force. If it succeeds in promoting global trade, this will undoubtedly lead to shifts in global trade patterns, which could open up new pathways for the movement of exotic and potentially invasive species.

There are several international agreements and institutions aimed at regulating and monitoring the movement of exotic species through trade – for example, the World Trade Organisation’s ‘Agreement on the Application of Sanitary and Phytosanitary Measures’, known as the SPS agreement, regulates trade risks to human, animal and plant health, as well as those associated with the trade of exotic species. International standards for importing animals, plants and food are set by three organisations – The World Organisation for Animal Health (OIE), the International Plant Protection Convention (IPPC), and the Codex Alimentarius Commission. However, the implementation of these standards and regulations varies globally – previous studies have found that GDP and socio-economic indicators such as the amount of protected land, correlate with the invasive species introductions.

To find out if other aspects of a country’s socio-economics and development influence their risk of invasive species, researchers at the University of Wellington, New Zealand, made use of a 10-year database of exotic species seizures in New Zealand. From 2002 to 2011, 47328 exotic plants and animals were intercepted by quarantine officials in New Zealand. They found that governence and development of exporting countries had a significant impact on the rate of interceptions.

Exotic species carried in on plant matter such as fruit and vegetables, were significantly more likely to be imported from countries with poor regulation. Hardly surprising. Also rather unsurprisingly, they found that vegetable matter exported from countries with more forest cover (and presumably more biodiversity and more exotic species to potentially hitch a ride) was more likely to harbour exotic species.

What was surprising was that they found government corruption was negatively correlated with exotic species interceptions – the more corrupt the government, the fewer exotic species that managed to sneak in on plant imports.

Political stability and the level of adherence to laws were key factors influencing the import of exotic species carried in on timber products, as well as those carried in on vehicles.

The authors recommend a shift in quarantine procedures to focus on countries identified as high-risk based on socio-economic factors – high forest cover, poor regulation, low political stability and adherence to laws, and, bizarrely, low corruption. They offer two explanations for this bemusing result – companies in New Zealand who are importing goods from highly corrupt countries may be implementing there own regulatory procedures, masking the impact of corruption; or that more corrupt countries tend to be less economically active and may export less over all.

Selecting trade partners based on socio-economic factors could offer New Zealand a 9-fold reduction in the rate of exotic species introduction on imported vegetables, timber and vehicles.

The risk of exotic species introductions on commodities such as vegetables, timber and vehicles has changed significantly over their 10-year study. While vegetable matter and timber have improved – with fewer exotic species intercepted in 2011 than 2002 – vehicle imports have harboured increasing numbers of exotic species.

The risk of introduction of invasive species through trade is a complex issue which is influenced by regulation both internationally, nationally and at the organisation level, the ecological characteristics of a country, the patterns of trade and changes in the value and availbaility of different commodities, and also on the governance, development and politics of the country exporting the goods. The more of these factors that we can take into account when making policy changes, the more effective we will be in preventing invasive species introductions through trade.

Want to Know More?

• Brenton-Rule, Barbieri and Lester (2016) Corruption, development and governance indicators predict invasive species risk from trade Proceedings of the Royal Society B.
• Kaufmann, Kraay, and Mastruzzi (2010) The Worldwide Governance Indicators: Methodology and Analytical Issues. World Bank Policy Research Working Paper No. 5430.
• Hulme (2009) Trade, transport and trouble: managing invasive species pathways in an era of globalization. Journal of Applied Ecology
• Pimentel, Zuniga, and Morrison (2004) Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics
• Vilà, and Pujadas (2001) Land-use and socio-economic correlates of plant invasions in European and North African countries. Biological Conservation
• Vitousek et al (1997) Introduced species: a significant component of human-caused global change. New Zealand Journal of Ecology