Nuno Guiomar

The dynamics and drivers of fuel and fire in the Portuguese public forest

The assumption that increased wildfire incidence in the Mediterranean Basin during the last decades is an outcome of changes in land use warrants an objective analysis. In this study we examine how annual area burned (BA) in the Portuguese public forest varied in relation to environmental and human-influenced drivers during the 1943-2011 period. Fire behaviour models were used to describe fuel hazard considering biomass removal, cover type changes, area burned, post-disturbance fuel accumulation, forest age-classes distribution and fuel connectivity. Biomass removal decreased rapidly beyond the 1940s, which, along with afforestation, increased fuel hazard until the 1980s; a subsequent decline was caused by increased fire activity. Change point analysis indicates upward shifts in BA in 1952 and in 1973, both corresponding to six-fold increases. Fire weather (expressed by the 90th percentile of the Canadian FWI during summer) increased over the study period, accounting for 18 and 36% of log(BA) variation before 1974 and after 1973, respectively. Regression modelling indicates that BA responds positively to fire weather, fuel hazard and number of fires in descending order of importance; pre-summer and 2-year lagged precipitation respectively decrease and increase BA, but the effects are minor and non-significant when both variables are included in the model. Land use conflicts (expressed through more fires) played a role, but it was afforestation and agricultural abandonment that supported the fire regime shifts, explaining weather-drought as the current major driver of BA as well. We conclude that bottom-up factors, i.e. human-induced changes in landscape flammability and ignition density, can enhance or override the influence of weather-drought on the fire regime in Mediterranean humid regions. A more relevant role of fuel control in fire management policies and practices is warranted by our findings.

The effects of grazing management in montado fragmentation and heterogeneity

The Portuguese silvo-pastoral system montado is broadly classified as a High Nature Value (HNV) system since it corresponds to farmland hosting high biodiversity levels, and such biodiversity depends on specific land use practices. However, in recent decades a decline both in the total montado area and in the tree cover density within the montado has been observed, driven mainly by management changes. This decline may result in biodiversity loss. Grazing is a central aspect determining the long-term sustainability of the montado system and it has implications also on the montado structural diversity, particularly on connectivity and heterogeneity, which is crucial for the maintenance of montado HNV. The aim of this paper is to demonstrate how variations in montado structural diversity are correlated with grazing management and its implications on the value of the system for conservation. The empirical data derives from a case study composed of 41 montado farms in two municipalities of the Alentejo region. Data on grazing management, biophysical and spatial factors were collected and several metrics were calculated to assess montado fragmentation and heterogeneity. A multivariate analysis was performed using generalized additive models. Results show that different grazing patterns, depending on stocking density and grazing animal type, are correlated with variations in montado fragmentation and heterogeneity. Particularly, cattle’s grazing is shown to have adverse effects on the montado fragmentation, while sheep grazing is shown to have stronger impacts on the heterogeneity within the montado patches.

Assessing the effectiveness of RapidEye multispectral imagery for vegetation mapping in Madeira Island (Portugal)

Abstract Madeira Island is a biodiversity hotspot due to its high number of endemic/native plant species. In this work we developed and assessed a methodological framework to produce a RapidEye-based vegetation map. Reasonable accuracies were achieved for a 26 categories classification scheme in two different seasons. We tested pixel and object based approaches and the inclusion of a vegetation index band on top of the pre-processed RapidEye bands stack. Object based generally showed to outperform pixel based classification approaches except for linear or highly scattered classes. The addition of a vegetation index to the workflow increased the separability of the Jeffrey-Matusita least separable class pairs, but not necessarily the overall accuracy. The Pontius accuracy assessment highlighted class specific accuracy tradeoffs related to different combinations of the inputs and methods. The approach to be used, in conclusion, should be carefully considered on the basis of the desired result.

Using modeling tools for implementing feasible land use and nature conservation governance systems in small islands – The Pico Island (Azores) case-study

The present study deals with the development of systematic conservation planning as management instrument in small oceanic islands, ensuring open systems of governance, and able to integrate an informed and involved participation of the stakeholders. Marxan software was used to define management areas according a set of alternative land use scenarios considering different conservation and management paradigms. Modeled conservation zones were interpreted and compared with the existing protected areas allowing more fused information for future trade-outs and stakeholders involvement. The results, allowing the identification of Target Management Units (TMU) based on the consideration of different development scenarios proved to be consistent with a feasible development of evaluation approaches able to support sound governance systems. Moreover, the detailed geographic identification of TMU seems to be able to support participated policies towards a more sustainable management of the entire island.

Contributions of Iberian Silvo-Pastoral Landscapes to the Well-Being of Contemporary Society

ABSTRACT Assessments of societys perceptions of rangeland systems offer insights into the motivations, cultural beliefs, and values that can support landscape conservation and the everyday decisions of landowners. Silvo-pastoral landscapes, the grazed oak woodlands known as montado in Portugal and dehesa in Spain, are the main rangelands of southwestern Iberia. At the interface of complex interactions between natural processes and human activities, they have potential to deliver multiple services at the ecosystem level. However, the actual rendering of their potential to the well-being of contemporary society has not been comprehensively documented. This paper aims to enrich research perspectives and identify benefits and challenging aspects of silvo-pastoral landscapes through the lens of society well-being. An integrated socioecological perspective is used to examine one case study in Portugal and one in Spain. To better understand their context, montado and dehesa are assessed relative to other landscape types in the studied areas. A qualitative approach assesses tangible but also intangible aspects. The interviewed stakeholders include members of rural communities, public authorities, land managers, and researchers. Results reveal similar benefits and challenges in montado and dehesa. Interviewees considered them to have numerous sociocultural and environmental benefits. These were mainly regulatory services but also intangible benefits such as cultural identity, aesthetic qualities, and local knowledge. Nevertheless, a rendering of their full potential to society well-being has numerous challenges. These systems were believed to struggle economically, due to the low prices for the goods produced and a high dependence on subsidies. Their environmental vulnerability was also highlighted. Critical challenges for future research and policy interventions are identified for both case studies. Moreover, we encourage the wider application of approaches to rangelands focusing on well-being, as they provide a complement to ecological and economic perspectives that can improve understanding of social-ecological systems.

Estimating tree canopy cover percentage in a mediterranean silvopastoral systems using Sentinel-2A imagery and the stochastic gradient boosting algorithm

ABSTRACT The availability of accurate and updated spatial information of tree cover in semi-arid and arid silvopastoral systems (SPSs) is crucial to understand their spatial patterns and trends. Although remote-sensing techniques have been proved useful in estimating tree canopy cover in general, more research is required to investigate the capabilities of new high spectral and spatial resolution satellites, such as Sentinel-2A, in predicting tree canopy cover in semi-arid environments. The objective of this study was to explore the capabilities of Sentinel-2A multispectral data, in combination with a stochastic modelling technique, for mapping montado tree canopy cover percentage (CCP) at pixel level. The stochastic gradient boosting algorithm was used to predict tree CCP using Sentinel-2A spectral data, vegetation indices, and textural information as predictor variables. The results of the study showed that the combination of multispectral bands with the selected vegetation indices and grey-level co-occurrence matrix (GLCM) texture features performs well, presenting a coefficient of determination (R2) of 82.8% and an error prediction of 8.68%. The analysis also showed that normalized difference vegetation index (NDVI) and Plant Senescence Reflectance Index (PSRI), as well as homogeneity texture feature, were the most important predictor variables to undertake the complex montado tree canopy cover estimation. In addition, this study demonstrated the usefulness of narrow spectral bands provided by the Sentinel-2A sensor for accurately estimating tree CCP (e.g. Red Edge1 – B5 – for PSRI and NIR2 – B8a – for NDVI computation). The modelling procedure used here emphasizes the effectiveness of stochastic models for predicting tree canopy cover from a complex semi-arid silvopastoral system by using Sentinel-2A multispectral data.

Cattle-driven forest disturbances impact ensemble composition and activity levels of insectivorous bats in Mediterranean wood pastures

Abstract Forests can be modified by fine-scale disturbances such as those prompted by cattle grazing, but their impacts on biodiversity are far from being understood. Here, we investigate the response of insectivorous bats to cattle-driven forest disturbances, using a savanna-like Mediterranean agroforestry system, the Portuguese montado, as study system. In doing so, we compared bat ensemble composition and activity levels of bats across sites that differed in how frequently they were used by free-ranging cattle. Specifically, we selected sites regularly used by cattle (central places) and sites seldom used (grazing sites). We found strong between-site differences in both bat species composition and activity levels, with lower diversity and activity in central places compared to grazing sites. These response patterns, corresponded to marked between-site differences in tree cover, seemingly driven by cattle use given the lower levels of tree regeneration and vegetation productivity in central places compared to grazing sites. Our work therefore demonstrates that it is not only severe forest loss and fragmentation that has an impact on insectivorous bats, but also when these processes operate at fine spatial scales. We thus suggest that fine-scale forest disturbances, particularly those driven by recurrent cattle use, cannot be neglected in the conservation management of agroforestry systems. In this context, we propose some management strategies aimed at counteracting the impact of cattle-driven disturbances on biodiversity in general, and on insectivorous bats in particular.