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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 clearing. 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.

The Amazon floodplains cover approximately 10% of the Amazon Basin and are composed of predominantly anoxic sediments that may store large amounts of carbon. Our study combines 210 Pb derived sedimentation rates from four recently analyzed sediment cores (n 5 4) with previously published organic carbon (OC) burial estimates (n 5 18) to provide a broad, first order estimate of carbon accumulation in Amazon floodplain lakes. The OC burial rates were 266 6 57 g C m 22 yr 21. This rate is several folds greater than those reported for lakes in arctic, boreal, temperate, and tropical regions. The large amount and spatial variation of OC burial rates in these floodplain lakes highlights the need for increased sampling efforts to better measure these potentially important components of the Amazon Basin carbon budget. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Scientific Significance StatementIn the Amazon Basin, floodplains and the lakes within them are major sources of greenhouse gases. However, it is not known whether carbon burial in the floodplain lakes is large enough to offset their greenhouse gas emissions. Here, we show that Amazonian floodplain lakes can partly offset greenhouse gas emissions through significant carbon burial rates (266 6 57 g C m 22 yr 21) that are greater than any other measured lake type. By extrapolating our observations, we show that burial in Amazon floodplain lakes may play an important role in the carbon budget of the Amazon Basin.

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