Underexplored and growing economic costs of invasive alien trees

Abstract

The high ecological impacts of many invasive alien trees have been well documented. However, to date, we lacked synthesis of their economic impacts, hampering management actions. Here, we summarize the cost records of invasive trees to (I) identify invasive trees with cost information and their geographic locations, (II) investigate the types of costs recorded and sectors impacted by invasive trees and (III) analyze the relationships between categories of uses of invasive trees and the invasion costs attributed to these uses. We found reliable cost records only for 72 invasive trees, accumulating a reported total cost of $19.2 billion between 1960 and 2020. Agriculture was the sector with the highest cost records due to invasive trees. Most costs were incurred as resource damages and losses ($3.5 billion). Close attention to the ornamental sector is important for reducing the economic impact of invasive trees, since most invasive trees with cost records were introduced for that use. Despite massive reported costs of invasive trees, there remain large knowledge gaps on most invasive trees, sectors, and geographic scales, indicating that the real cost is severely underestimated. This highlights the need for further concerted and widely-distributed research efforts regarding the economic impact of invasive trees.

Figure 1

Spatial distribution of recorded costs of invasive trees. The map shows with a color categorical gradient the countries with the highest (black) to lowest (cream) cost recorded (‘observed’ and ‘highly reliable’ costs; 2017 US Dollars) of invasive trees. Countries without observed cost reports are in white. The map also indicates the number of references reporting costs of invasive trees by country with the green node size.

Figure 2

Costliest families and genera. Top ten costliest families of invasive trees and the respective costliest genera of the top five families considering highly reliable, observed costs records (in 2017 US$ billions). Different colors indicate different families and shades distinguish genera.

Figure 3

Sectors affected and type of cost. Total costs (highly reliable and observed) of invasive alien trees according to (a) impacted sector and (b) type of cost.

Figure 4

Uses of invasive trees with cost records. Tree height shows the number of invasive tree species for each category of use and the number on top shows the total cost incurred (highly reliable and observed), also indicated by shades of green with darker green representing higher costs (see text for details).