Marbled murrelets are seabirds that nest exclusively in old-growth forest, making logging the primary conservation and welfare threat.
Murrelet welfare depends entirely on old-growth forest availability. Without adequate nesting habitat, breeding failure occurs and birds expend energy commuting to unsuitable sites. The loss of nesting sites from logging eliminates reproductive success across large areas simultaneously. Old-growth logging that has taken centuries to grow eliminates nesting habitat irreversibly on human timescales. Conservation of remaining old-growth directly prevents the reproductive failure welfare harm that population decline represents.