In the early 1960s, after Bonham-Christie's death, Brotherton organized a group to oppose development on Brownsea Island, because the planned development would threaten a wading birds habitat.
A comezos da década de 1960, despois da morte Bonham-Christie, Brotherton organizou un grupo para opoñerse ó desenvolvemento da illa Brownsea, xa que ameazaba o hábitat de aves ameazadas.