Plants Prove Key
Using images from the Landsat satellites and the National AgricultureImagery Program, Stephen and his NEXUS graduate student,Mohammad Masih Edalat, investigated the land surface changes at three sites: the Ivanpah Solar Electric Generating System in California, the Nellis Solar Power Plant in Clark County, Nevada and the Nevada Solar One site near Boulder City, Nevada.
Inspecting the satellite data, the team found that the installation changed the albedo-the ability of the land to reflect light-of the land surface within the sites both during and after construction.
“If there was pre-existing vegetation and that vegetation was removed and bare soil was exposed, that will show up as a change in the albedo of the surface,” Stephen says.
The scientists observed that the bladed land reflected more light, that can contribute to lower temperatures within the sites. The panels themselves also reflected light and created shadows further cooling the land.
In addition to this impact, the scientists noticed that concrete buildings and roads also increased the reflectivity of the land surface. But outside of the installation site, the findings proved surprising.
“We thought there’d be a halo effect of the facility,” Stephen says. “In the immediate vicinity we would see some impact on the albedo and as you go farther away that impact reduces.”
Instead the researchers found almost no impact on the reflectivity or temperature immediately outside of the facilities. “What we are finding is that the facility itself has it’s primary impact when it is built but we are not seeing any secondary effect other than the road network that is built to get there,” Stephen says. “We’re not seeing any secondary effects on the neighboring vegetation or neighboring soil.”
For arid regions, the news is good, but Stephen emphasizes that the impacts might prove more significant when more plants existed prior to installation. When Stephen’s undergraduate student James Reynolds looked at the impacts of solar installation in less arid regions he found greater changes in the surrounding environment. The findings imply that it is the removal of vegetation, rather than changes in reflectivity, which truly impact the ecosystem.
“So one of the take home messages is that when any of these facilities is being constructed, care should be given in recognizing how is the vegetation impacted because that will have impact on pretty much every ecosystem-related aspect in that area,” Stephen says.