Final answer:
The inability to control invasive species is due to their high reproductive rates, adaptability, and the fact that control methods like removal or pesticides require repeated application. Additionally, biological controls can fail and might harm native species. New research-based ecological approaches show promise but are not yet widely implemented.
Step-by-step explanation:
Scientists face significant challenges in controlling invasive species mainly because these species can proliferate across diverse ecosystems, adapt to new environments, and often have high reproductive rates. Efforts to eradicate or control them, such as physical removal or the use of pesticides, must often be repeated indefinitely, as these strategies don't typically lead to permanent solutions. Additionally, biological controls like introducing predators or pathogens to combat these invaders can fail or cause harm to native species. Invasive species can also continue to thrive due to climate change and human activity, including transportation and trade, which exacerbates the problem by introducing species into ecosystems where they have no natural predators.
An ecological approach to invader control, which involves comprehensive research into the invader's biology, has shown promising results in specific case studies. For example, understanding the biology and impact of invasive cane toads in Australia has led to the development of novel control methods. However, such strategies are still in the research phase and are not ready for large-scale deployment.