Coupling marine ecosystem state with environmental management and conservation: A risk-based approach

\ua9 2024 The Author(s)The sustainability of marine ecosystems demands a focus on ecological improvement, necessitating managers and conservationists to consider a range of actions from those that limit stressors to those that actively restore. Deciding the most appropriate action should be informed by environmental context, which includes assessing information on both degradation and recovery potential. Here, we provide an analysis of how the degree of ecological degradation coupled with the stressor regime can inform environmental management and conservation actions (e.g., stressor reductions, adaptive management, assisted recovery/restoration). With this analysis we design a risk framework combining principles that define ecosystem resilience and recovery times with those that characterize stressor regimes (i.e., the number, type, and impact). The combination of these principles defines where an ecosystem is placed along sliding scales of degradation and recovery and likely response to protective and restorative interventions. It is designed to facilitate place-based conversations regarding the risks of different management actions informed by the temporal dynamics of ecosystem degradation and recovery

The dynamics of expanding mangroves in New Zealand

In contrast to the global trend of mangrove decline, New Zealand mangroves are rapidly expanding, facilitated by elevated sediment inputs in coastal waters as a consequence of large-scale land use changes following European settlement. New Zealand mangroves are at the southern limit of the global mangrove extent, which limits the tree height of Avicennia marina var. australasica, the only mangrove species present. Mangroves in New Zealand thrive in the sheltered environments of infilling drowned river valleys with abundant supply of fine terrigenous sediments, showing various stages of mangrove succession and expansion dynamics. Bio-physical interactions and carbon dynamics in these expanding temperate mangrove systems show similarities to, but also differ from those in tropical mangrove forests, for instance due to the limited height and complexity of the mangrove communities. Likewise, ecosystem services provided by New Zealand mangroves deviate from those offered by tropical mangroves. In particular, the association of mangrove expansion with the accumulation of (the increased supply of) fine sediments and the consequent change of estuarine ecosystems, has provoked a negative perception of mangrove expansion and subsequently led to mangrove clearance. Over recent decades, a body of knowledge has been developed regarding the planning and decision making relating to mangrove removal, yet there are still effects that are unknown, for example with respect to the post-clearance recovery of the original sandflat ecosystems. In this chapter we discuss the dynamics of New Zealand’s expanding mangroves from a range of viewpoints, with the aim of elucidating the possible contributions of expanding mangroves to coastal ecosystem services, now and in the future. This chapter also reviews current policies and practice regarding mangrove removal in New Zealand and addresses the (un)known effects of mangrove clearance. These combined insights may contribute to the development of integrated coastal management strategies that recognise the full potential of expanding mangrove ecosystems