Because invasive trees and shrubs are known to have significant impacts on invaded communities (Jäger et al. 2009; Watling et al. 2011), more concentrated research efforts should be dedicated to evaluating their effects, despite the additional time and effort required for research on long-lived species.
A number of issues require further investigation and addressing them should be a key priority for research on the impacts on invading alien plant species on river flows and groundwater resources.
While many nonnative species have little to no measurable impact on their invaded regions, a few have caused great economic and ecosystem harm.
Further, the large context dependency of both invasion events, the magnitude of impact on the invaded systems as well as the extent to which the impacts are reversible or irreversible makes it difficult to devise a generalized scheme of prediction.
Several ascidian species have been identified as invasive species, such as Styela clava and Pyura praeputialis [ 23- 26], and have a strong ecological impact on the invaded marine ecosystems.
We discuss which features of invasive species and invaded systems determine the probability of irreversible impacts on the invaded ecosystem.
Ecosystem transformers that changes pools of energy and elements, e.g. N-fixing plants in N-limited systems, or ecosystem engineers, i.e. earthworms, that physically re-organize the invaded ecosystem are therefore more likely to cause long-term or irreversible impacts on the invaded ecosystem.
However, the negative impacts of H. mantegazzianum on invaded ecosystems may actually only be temporary.
These issues become readily apparent for non-model invasive species, whose importance is heightened due to the environmental and ecological impacts on the invaded regions.
L. humile has had mostly negative effects on invaded ecosystems.
