NEW YORK — For the past two decades, Sara Fern Fitzsimmons has raised seedlings of the American chestnut in research orchards along the Eastern Seaboard, keeping them fed and hydrated and charting their growth. At the turn of the 20th century, the “redwoods of the East” dominated forests with their towering trunks, accounting for an estimated one in every four trees from southern Maine to northern Florida. They fueled a major timber industry, and their nuts were a vital source of food for both livestock and countless families. As one historian wrote, the tree “was possibly the single most important natural resource of the Appalachians.” …A breakthrough in genetic engineering was intended to bring them back and transform the science of species restoration while potentially netting its inventors millions of dollars and wide acclaim. Instead, a mix-up in the lab has sparked a veritable civil war in the niche conservation community.