Percorrer por autor "Cunha, Alexandra"
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- Global analysis of seagrass restoration: the importance of large-scale plantingPublication . van Katwijk, Marieke M.; Thorhaug, Anitra; Marba, Nuria; Orth, Robert J.; Duarte, Carlos M.; Kendrick, Gary A.; Althuizen, Inge H. J.; Balestri, Elena; Bernard, Guillaume; Cambridge, Marion L.; Cunha, Alexandra; Durance, Cynthia; Giesen, Wim; Han, Qiuying; Hosokawa, Shinya; Kiswara, Wawan; Komatsu, Teruhisa; Lardicci, Claudio; Lee, Kun-Seop; Meinesz, Alexandre; Nakaoka, Masahiro; O'Brien, Katherine R.; Paling, Erik I.; Pickerell, Chris; Ransijn, Aryan M. A.; Verduin, Jennifer J.In coastal and estuarine systems, foundation species like seagrasses, mangroves, saltmarshes or corals provide important ecosystem services. Seagrasses are globally declining and their reintroduction has been shown to restore ecosystem functions. However, seagrass restoration is often challenging, given the dynamic and stressful environment that seagrasses often grow in. From our world-wide meta-analysis of seagrass restoration trials (1786 trials), we describe general features and best practice for seagrass restoration. We confirm that removal of threats is important prior to replanting. Reduced water quality (mainly eutrophication), and construction activities led to poorer restoration success than, for instance, dredging, local direct impact and natural causes. Proximity to and recovery of donor beds were positively correlated with trial performance. Planting techniques can influence restoration success. The meta-analysis shows that both trial survival and seagrass population growth rate in trials that survived are positively affected by the number of plants or seeds initially transplanted. This relationship between restoration scale and restoration success was not related to trial characteristics of the initial restoration. The majority of the seagrass restoration trials have been very small, which may explain the low overall trial survival rate (i.e. estimated 37%). Successful regrowth of the foundation seagrass species appears to require crossing a minimum threshold of reintroduced individuals. Our study provides the first global field evidence for the requirement of a critical mass for recovery, which may also hold for other foundation species showing strong positive feedback to a dynamic environment.Synthesis and applications. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration.For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration.
- A survey-based assessment of seagrass status, management and legislation in EuropePublication . de los Santos, Carmen B.; Sigurðardóttir, Ragnhildur; Cunha, Alexandra; Cook, Kevan; Wiktor, Józef M.; Tatarek, Agnieszka; Santos, RuiSeagrass meadows are ranked amongst the most productive ecosystems on Earth, providing high-value ecosystem services in coastal areas. Yet, seagrass habitats are declining worldwide at an unprecedented rate as a consequence of both anthropogenic and natural pressures, which suggests an inefficient management. Seagrasses are widespread along European coasts and the knowledge on their conservation status and management has been increased in the last decade although an overall view for the whole Europe is lacking. The general aim of this survey-based study was to assess the present status of seagrass habitat conservation, management and legislation in Europe based on the expert judgement of 25 participants from 19 coastal European countries. We specifically assessed the seagrass ecological status and their major threats; the level of awareness; the effort in mapping, monitoring and restoration; and the state of management plans and policy in each country. We furthermore reviewed the legislation for seagrass habitats in order to assess the protection status of seagrasses in Europe. The survey-based assessment revealed great differences among seagrass species and countries regarding their awareness, ecological status, mapping, monitoring and management. Several good examples of seagrass management, in cooperation with scientists, were identified although many countries still lack the fundamental tools for a proper management. A consistent body of legislation was compiled for most European countries, yet their implementation was reported to be rather variable and weak. The results of this study will provide guidelines for a more effective seagrass management and policy in Europe.