Fragmentation poses one of the greatest threats to tropical forests, with short-term changes to the structure of forest canopies affecting microclimate, tree mortality, and growth. The long-term effects of fragmentation are poorly understood because: (1) most effects require many decades to materialize, but long-term studies are very rare; (2) the effects of edges on forest canopy structure as a function of fragment size are unknown; and (3) fragmentation studies are often confounded by various factors that are difficult to control. Forest Service scientistsquantified the long-term (centennial) effects of fragmentation on forest carbon storage, productivity, and canopy structure using ground-based sampling and airborne light detection and ranging (LiDAR) of Hawaiian montane forest fragments. The fragments, which ranged in size from 0.02 to 1,000 hectares (1 hectare = 2.47 acres), were created more than 130 years ago by flowing lava. The scientists found that carbon storage in above ground living biomass and in coarse woody debris declined dramatically with decreasing fragment size, as did stand productivity. Forest canopy structure varied strongly between forest fragment center and edge, and between large and small fragments, becoming gappier in edges and in small fragments. Finally, nutrient return through litterfall declines as fragment size declines, indicating stronger nutrient losses from small versus large fragments. These changes caused by long-term fragmentation highlight the ecosystem benefits of maintaining large versus small fragments, and complement conservation biology findings from this system and elsewhere that large fragments more effectively support native biodiversity compared with small fragments.?