Tomoaki Miura (center) in the field with his graduate students Joshua Turner (left) and Alex Dale (right).

Invasion by alien, exotic plants is one of the most significant threats to ecosystems around the world. Hawai‘i is particularly susceptible because of the islands’ long history of infrequent exposure to foreign ecological disturbances and the resulting reduced resilience of its native species in withstanding such invasions. Fireweed (Senecio madagascariensis) is one of the most highly invasive weeds in Hawai‘i, and its ecological and economic impacts on pasture and rangelands—and the livestock production they support—can be devastating.

Tomoaki Miura, assistant professor in CTAHR’s Natural Resources and Environmental Management department, has taken on this ecological foe. A native of Kanagawa, Japan, with a BS in earth science, an MS in resource management, and a PhD in soil and water science—with double minors in remote sensing and statistics—Miura joined CTAHR in 2003. Since then, his ability to collaborate has enabled him to develop thriving research projects and become fireweed’s worst enemy.

More information on fireweed management is on a video by CTAHR’s James Leary.

Miura is a member of a multi-disciplinary team formed by CTAHR livestock specialist Mark Thorne. The team consists of CTAHR researchers, MS students, and Cooperative Extension agents in statewide collaboration with USDA-ARS researchers. Together, they characterized the invasion ecology and population dynamics of fireweed, and then they developed remote-sensing methods to detect and map fireweed populations. After initially unsuccessful attempts to map fireweed using satellite imagery, Miura and Roland Thompson, PhD candidate in UH Manoa’s Department of Urban and Regional Planning, developed a cost-effective, high-resolution digital camera system that allows them to focus at a spatial resolution as small as 5 mm and has since been applied over wide areas susceptible to fireweed invasion.

Then, taking the project a step further, Miura partnered with Alex Dale, an MS student in NREM, to produce an image-processing algorithm that, applied to the remote-sensing photos, successfully detects and maps areas covered with fireweed flowers. The team’s plan is to correlate these estimates of flower cover with ground measurements of fireweed population density to allow the airborne digital camera system automatically to determine the weed’s population density.

View CTAHR publications on fireweed,
Fireweed Control: An Adaptive Management Approach
Control of Madagascar Ragwort (aka Madagascar fireweed, Senecio madagascariensis)