The impacts of land-use changes on the recovery of saltmarshes in Portugal

Abstract

Human-induced land-use changes have resulted in loss and degradation of intertidal environments worldwide. Saltmarsh ecosystem dynamics in Portugal are greatly influenced by historic uses and consequent habitat degradation. This study uses an original approach combining vegetation surveys and spatial analysis of historic maps and aerial photographs to assess the effects of land use changes on saltmarshes in two areas in the Algarve, southern Portugal. Historical maps from c. 1800 and aerial photographs from 1958 to 2010 were analysed to map saltmarsh ecosystems and quantify land-use changes in the Alvor estuary and Arade River. Between c. 1800 and 2010 more than half of saltmarshes were lost due to dyke building and saltmarsh reclamation for agriculture. In mid-1960s, the abandonment of reclaimed agricultural areas resulted in the recolonization of saltmarsh vegetation, which developed physically separated from natural marshes. In the study area, these saltmarshes naturally evolved into two distinct typologies: (1) enclosed mixed marshes, formed by patches of brackish, freshwater and some invasive species developing due to saline intrusion in areas where dykes have not been breached; and (2) tidally-restored saltmarshes, formed in areas where dyke breaching allows incursion of tides and development of a vegetation structure similar to natural saltmarshes. In Europe, passive (without human intervention) and active (artificially planned) saltmarsh restoration are important mechanisms for voluntary or statutory re-creation of intertidal habitats. Improved understanding of the factors influencing the development of distinct saltmarsh typologies through passive ecosystem recovery can provide new insights to support decision-making concerning intertidal habitat restoration.

Examining change in complex social-ecological systems using multiple long-term records: the New Forest – a case study

“…-in the investigation of long-term system change and the extent to which modern-day landscapes are a product of past land use and management strategies (e.g. Hjelle et al [34], Sigurmundsson et al [54], McCune et al [63], Feurdean et al [64], Almeida et al [65]).…”

Managed Realignment : A Viable Long-Term Coastal Management Strategy?

“…In the USA and France there are In France, Spain and Portugal restoration of tidal flow into embanked areas occurs mainly as a result from accidental breaches due to storms or natural decay of abandoned defences (e.g. Cearreta et al, 2013;Almeida et al, 2014). In many cases, there is the view that restoration of natural habitat under these conditions produces similar results to managed 124 realignment (e.g.…”

The joint effect of tidal barrier construction and freshwater releases on the macrobenthos community in the northern Yellow River Delta (China)

“…Numerous researchers have focused on the resulting changes in the shoreline and associated habitats (Aubanel et al, 1999;Reise, 2005;Vos and van Kesteren, 2000), variations of soil physicochemical properties (Mora and Burdick, 2013;Tang et al, 2013), vegetation succession (Almeida et al, 2014;Piesschaert et al, 2005), and hydrological conditions (Carol et al, 2014). In addition to these characteristics of the coastal wetlands, turnover of the species that live in coastal watersheds and salt marshes is common, as these species are often highly vulnerable to human activities (Braeckman et al, 2014;Gordon, 1994).…”