CALIFORNIA — When ferocious wildfires tore through California’s prized giant sequoia forests, they killed towering trees that have lived there for thousands of years — and perhaps changed the nature of the groves forever. Now the US National Park Service (NPS) wants to give Mother Nature a helping hand, planting lab-grown seedlings it says will kick-start the return of these magnificent stands. “The goal is to reestablish enough sequoias in the first few years after fire so that we have trees 60, 100, 400 years from now,” says Christy Brigham, chief of resources management and science at Sequoia and Kings Canyon National Parks. …Andrew Bishop, a restoration ecologist at the NPS, says two or three years on from the fires there are some self-seeded plants, but nowhere near enough. …”There are serious downsides and risks to planting,” says Chad Hanson, a research ecologist and the director of the John Muir Project.