Construção e aplicação de uma ferramenta de avaliação de dinâmicas de paisagens

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Supporting the spatial management of invasive alien plants through assessment of landscape dynamics and connectivity

Publication . Machado, Rui; Duarte, Liliana Neto; Gil, Artur José Freire; Sousa‐Neves, Nuno; Pirnat, Janez; Santos, Pedro

Invasive alien species are responsible for several negative impacts worldwide. Managing biological invasions is often difficult and the success rate is quite low, but with good planning it is possible to achieve good results. Besides employing the correct methods and techniques, an overall strategy based on landscape dynamics and expected spatial patterns can be fundamental to achieve success. The decision of where to act can be embedded in a general strategy based on several criteria/goals such as control of large populations, connectivity disruption, and so on. This work focused on Acacia dealbata in a Natura 2000 site in Portugal, how the current amount and distribution can affect the spread pattern, and different possible strategies to approach the management. Based on the species dispersal traits, we argue that not only the area but also the perimeter (therefore, the shape) and location of the patches should be considered when fighting the invasion. Three scenarios were designed and compared using the perimeter–area ratio, a landscape dynamics analysis, and a connectivity index. Results show that removing the patches with higher perimeter–area ratio (mostly small satellite patches) would be more impactful than removing the larger patch or removing random intermediary perimeter–area patches first. After this approach based on landscape dynamics, the employment of a connectivity assessment provided an ordered list of patches to remove sequentially. Overall, this approach can be valuable in the early steps of the planning process, supporting better decisions regarding the available resources and contributing to maximize the effectiveness of the action.

2022-07Journal article

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Using graph theory to analyse and assess changes in Mediterranean woodland connectivity

Publication . Machado, Rui; Godinho, Sérgio; Guiomar, Nuno; Gil, Artur José Freire; Pirnat, Janez

CONTEXT The Portuguese montado is an agro-silvopastoral system, similar to the Spanish dehesa, known for its cultural, economic and ecological value. Despite its importance, contrasting processes such as land abandonment and land use intensification, together with several other factors, have been responsible for montado degradation in the last decades. Biodiversitywise, assuring high levels of connectivity is vital for many species that, in turn, contribute to the natural processes on which a healthy and sustainable montado relies. OBJECTIVES To study the montado connectivity in the recent decades and infer what the changes represent to the short and medium dispersal species regarding habitat availability. METHODS The study was conducted in an area delimited by biogeographic boundaries in Southern Portugal where montado is abundant. We used a graph theory based approach and montado maps of 1984, 1999 and 2014 derived from remote sensing. RESULTS The results show a loss of montado associated to increasing fragmentation over time. This led to a global connectivity decrement likely to have negative implications for montado species. The most affected species are those more dependent on habitat characteristics, such as forest specialist birds, and those with low mobility that have lost great amounts of habitat not only due to montado loss but also due to the increasing fragmentation that makes suitable patches unreachable. CONCLUSIONS Given the montado environmental relevance, measures should be taken in order to stop its loss and preserve the core areas that have guaranteed the connectivity over time.

2020-04Journal article

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