Complex sentence: Atop the highest peaks, above the tree line, there is a total of 87 acres (352,000 m²) of extraordinarily fragile alpine ecosystem; the amount of this ecosystem is constantly changing due to variation in the climate from year to year.
Split into simpler sentences: Atop the highest peaks, there is a total of 87 acres (352,000 m²) of extraordinarily fragile alpine ecosystem above the tree line. This environment may be changing due to variation in the climate from year to year.