There's no question that finding new sources of renewable energy is good for the environment. Less pollution and fewer greenhouse gases are good for people, plants, and animals. But clean energy sources can still cause problems. Wind turbines can get in the way of migrating birds and bats, for example. Some estimates say hundreds of thousands of these animals may die each year from collisions with the massive spinning blades.

But solar and wind power has another downfall: They're not always available. The sun only shines during the day and the wind comes and goes. There are very few places where the wind is constant enough to generate electricity all the time. And as easy as it sounds, storing energy for later use has proven a major challenge.

As anyone who's stayed near a beach can tell you, waves crash onto shore morning, noon and night. And that makes them ideal for generating energy around the clock. Now scientists are figuring out just how much energy waves could offer. But with this new ideology, some concerns have arisen.

One concern is about any ecological impacts of absorbing all of that energy from incoming waves. After all, that's how they generate electricity - by converting wave energy into electrical energy. Energy tapped from the waves will reduce how much energy will remain as the waves continue in toward shore. They will be smaller, at least for some distance. Smaller waves could lead to less mixing of nutrients within the water column; that's the water between a particular bit of ocean bottom and the surface above it. And that could impact with species that live there, Greaves says. "But it can also be a benefit," she adds. After all, "wave-energy converters can help provide some coastal protection" by reducing erosion.

The electric generators also could affect how wildlife interact. Many birds and marine mammals hunt for fish in areas that might be ideal sites for wave converters. It's possible that converters could even attract fish to them if the smaller critters they eat seek refuge there. That could, in turn, attract hungry predators. This might help boost marine life in the area. But fish, seals, and other animals might also get tangled up in long cables that anchor surface-floating energy converters. So researchers must study where they want to install these converters to make sure they won't harm local ecosystems.

Another concern is that the converters will make noise. This can be a problem for fish, dolphins and other animals that rely on sound to find food or to communicate. The deep rumble of a boat and the loud ping of sonar cause all kinds of problems for ocean animals. These creatures may struggle to find food or become disoriented. However, Greaves says, wave converters are unlikely to create high levels of noise. The noisiest part would happen when the converters are initially installed at some site. Once they start running, they should be fairly quiet.

On the plus side, converters might become the base for an artificial reef if algae, mussels, barnacles or corals take hold of the structure and begin to grow. Such reefs provide protection for fish and other marine life. That could increase the diversity of marine life in the area. They could be helpful, as long as those critters don't interfere with the wave converter's movement.

"From the vast resources of the ocean, wave energy has the potential to make a huge contribution towards our clean energy needs of the future," Greaves says. But, she cautions, it "needs to be done in a sustainable way, in harmony with the marine environment."