Final answer:
Invasive grass species, such as African molassesgrass and tropical American tufted beardgrass, have been observed actively spreading fire and changing fire regimes in different ecosystems.
Step-by-step explanation:
The species that has been observed actively spreading fire are invasive grasses, such as African molassesgrass and tropical American tufted beardgrass. These grasses dramatically increase fire frequency and intensity, leading to negative ecological consequences. For example, the invasion of the Florida Everglades by Australian paperbark trees, which catch fire easily and produce hotter fires, has resulted in changes to the ecosystem. Introduced species can have a significant impact on the fire regime and can transform entire ecosystems. Invasive grasses increase fire activity and change fire regimes by creating a cascade of negative ecological consequences. They increase fire frequency and intensity, which can have detrimental effects on species and ecosystems. The spread of invasive grasses is observed in various locations, such as the Florida Everglades and Hawaii. These grasses replace native vegetation and change the landscape from woodland to grassland or vice versa. In summary, invasive grass species, such as African molassesgrass and tropical American tufted beardgrass, have been observed actively spreading fire and changing fire regimes in different ecosystems.