Plant invasions in China - challenges and chances

Abstract

Invasive species cause serious environmental and economic harm and threaten global biodiversity. We set out to investigate how quickly invasive plant species are currently spreading in China and how their resulting distribution patterns are linked to socio-economic and environmental conditions. A comparison of the invasive plant species density (log species/log area) reported in 2008 with current data shows that invasive species were originally highly concentrated in the wealthy, southeastern coastal provinces of China, but they are currently rapidly spreading inland. Linear regression models based on the species density and turnover of invasive plants as dependent parameters and principal components representing key socio-economic and environmental parameters as predictors indicate strong positive links between invasive plant density and the overall phytodiversity and associated climatic parameters. Principal components representing socio-economic factors and endemic plant density also show significant positive links with invasive plant density. Urgent control and eradication measures are needed in China's coastal provinces to counteract the rapid inland spread of invasive plants. Strict controls of imports through seaports need to be accompanied by similarly strict controls of the developing horticultural trade and underpinned by awareness campaigns for China's increasingly affluent population to limit the arrival of new invaders. Furthermore, China needs to fully utilize its substantial native phytodiversity, rather than relying on exotics, in current large-scale afforestation projects and in the creation of urban green spaces.

Figure 1. Distribution and recent spread of invasive species.

Recent spread and resulting species density (log species richness/log area) and proportion of invasive plant species in China's provinces (A: Increase (%) in the number of invasive plant species in each province between 2007 and 2012, B: Species density of invasive plant species newly recorded in the respective province after 2007, C: species density of all invasive species, D: species density of invasive annual and biennial herbs, E: species density of invasive perennial herbs, F: species density of woody invasive species, G: Contribution (%) of invasive plants towards the total species number in each province, H: Species density of exotic tree species currently not recognized as invasive in China, but reported as invasive species in either the USA or Europe).

Figure 2. Main socio-economic and environmental gradients in China.

Comparison of China's provinces in relation to key socio-economic and environmental gradients, represented as Principal Components (A: PC1 chiefly representing overall plant species density and associated environmental parameters, B: PC2 linked closely to the socio-economic status and cropland proportion of each province, C: PC3 representing species density and proportion of endemic plants and seasonal temperature variation, D: PC4 representing recent changes in socio-economic conditions, E: PC5 mirroring per capita GDP).

Figure 3. Shifts in invasive species distribution in relation to main socio-economic and environmental gradients.

Ordination plot based on the redundancy analysis of invasive plant species distribution and the five principal components representing socio-economic and environmental factors (A: triplot combining principal components (arrows), provinces and invasive species, B: biplot combining principal components and invasive species, differentiated into different life forms).