Relationship Between Landscape Pattern and Human Disturbance from 1990 to 2018 in Mainland Portugal

Abstract

The land use/land cover pattern of landscapes as the main element of the landscape structure has an important role in landscape management, nature conservation, and preservation, considering its ability to provide valuable information about the spatial distribution and changes in land cover that occur on the Earth's surface. On the other hand, human activities have caused significant impacts on ecosystems, resulting in a loss of biodiversity, increased risks of erosion and soil degradation, and wildfires. In the last few decades, the growing trend of occurrence of negative effects on land use/land cover has not contributed to the achievement of sustainable development goals (SDGs), considering that the relationship between humankind and the environment is an extremely fragile equilibrium. In recent decades, large-scale land use and land cover (LULC) patterns have shown stability, but there have been significant dynamics observed specifically in forest areas and agricultural land. Among these changes, the conversion of maritime pine to eucalyptus stands out as the most relevant transition in terms of forest and agroforestry use classes. This conversion is a result of economic incentives available, which have contributed to the gain in forested areas. This study intends to verify how the alteration of the landscape configuration, represented by different metrics of configuration and diversity, is related to the intensity of human disturbance. The objectives of the study are: (1) to quantify the change in land use/land cover (LULC) patterns and the degree of human disturbance in Mainland Portugal between 1990 and 2018, and (2) to study the relationship between LULC configuration and the impact resulting from human disturbance under different levels of intensity, to understand how changing trends in landscape pattern can serve as indicators to estimate landscape changes resulting from human actions. The Hemeroby index (HI) was calculated to quantify the impacts on ecosystems resulting from disturbance caused by human actions. Based on the Hemeroby index value analysis for the period between 1990 and 2018, the level of naturalness increased in 58% of the country, mainly in the south and east of Portugal. The landscape pattern was quantified using a set of metrics, namely Mean Patch Size (MPS), Mean Shape Index (MSI), Total Edge (TE), Mean Patch Fractal Dimension (MPFD), and Mean Perimeter-Area Ratio (MPAR). To identify the existing statistical correlations between the geometric parameters of the landscape and the HIs values, the Spearman method was used. At the landscape level, the metrics TE and MSI have a strong negative correlation with HI. This suggests that landscapes with greater structural complexity are good indicators of low levels of hemeroby. At the class level, edge density (ED) and mean patch size (MPS) showed a significant correlation with the Hemeroby index for seminatural areas (all metrics), artificial surfaces and forests (TE, MSI, and MPS), agricultural areas (TE, MPS, and MPFD), and Bare Ground (TE, MSI, and MPFD).