THE REGIONAL IMPACT OF AN INVASIVE SPECIES, JAPANESE KNOTWEED, ON SURFACE WATER SYSTEMS

The introduction and spread of invasive plant species have long been recognized as having the potential to severely impact and alter biologic and physical systems. These plant species have increased their range both from unintentional and intentional human introduction and by opportunistically colonizing habitat shifts caused by climate change. Invasive plants have shown the ability to affect surficial and shallow groundwater resources, but research on this has typically been focused on arid regions, such as the southwestern United States.

We demonstrate in this project that the invasive plant species, Japanese knotweed, has the physiological characteristics to impact hydrologic systems in mesic areas such as the eastern United States. Japanese knotweed has the ability to extract large amounts of water from riparian areas, even during water-limited times. This project mapped Japanese knotweed distribution at several sites using public areas and road crossings in northern New Jersey to be able to extrapolate Japanese knotweed coverage at the watershed scale. Japanese knotweed water use was measured through short-term, intensive field and laboratory measurements in a companion study. The results show that in northern New Jersey Japanese knotweed has the ability to negatively impact river discharge, affect biologic habitat, and possibly restrict regional water supplies. Northern New Jersey is part of the larger Highlands Region, which is the critical source area for drinking water that serves over 5 million people in New Jersey and millions more in New York City. The potential future impact of invasive plant species such as Japanese knotweed is magnified when projected climate change scenarios already show decreased precipitation and increased evapotranspiration for the region.