Conserving large old trees as small natural features

Abstract

In many ecosystems globally, large old trees occur as single, spatially isolated individual trees or as small groups of scattered trees and can therefore be considered to be small natural features. Despite being constrained spatially, individual large old trees and small stands of such trees nevertheless play numerous critical ecological roles (e.g. in carbon storage and provision of wildlife habitat). The protection and management of large old trees as small natural features is essential to maintain these roles and will often require targeted fine-scale conservation strategies. Such strategies can include bans on cutting trees above a certain size, micro-fencing to control threats associated with livestock grazing, and buffers comprised of other vegetation to limit the impacts of fire and chemical sprays. Effective conservation to mitigate the effects of factors threatening large old trees will often demand ecosystem-specific responses. This is because the drivers of loss will often manifest in ecosystem-specific ways. Three general principles will likely apply in almost all cases: (1) Protect existing individual large old trees; (2) Reduce rates of adult mortality. This is because adult mortality is a key part of the life cycle of large old trees; increased adult mortality can lead to population crashes; and (3) Ensure there are sufficient recruits of trees of varying ages to replace existing large old trees as they eventually die.