Climate pressure

Global Climate Change will seriously affect the hydrological processes and alter the supply of ecosystem services that are vital to human well-being. Climate change is expected to affect precipitation and evapotranspiration patterns, and consequently variables such as local water availability, river discharge, and the seasonal availability of water resources. The latest state of the art review on climate change research for the Mediterranean region by shows that recently observed trends and projections from climate model ensembles indicate a strong susceptibility to change in hydrological regimes, an increasing general shortage of water resources and consequent threats to water availability and management. Based on the longest available records, all Study Sites display clear trends of moderate temperature increase. These trends are manifested with variable degrees of drought related stresses, from constant to seasonal and from long-established to contemporary. Taking into account the uniformly positive temperature trends that appear to agree with climate change scenarios, there is a high probability that these conditions will aggravate in the future.

Grazing pressure

The extraction of animal products effectively reduces the net organic carbon and nutrients from the natural ecosystem and, depending on the extraction rate, can potentially deplete the rangeland soil services. In overexploited rangelands, vegetation removal and trampling by livestock promotes soil erosion by water through disintegration of biological topsoil that is an active site of soil formation and organic matter decomposition. The latter can cause surfaces to seal with a mineral film that reduces infiltration and contributes to soil-eroding flashfloods, thus leading to land degradation. In this mechanism of land degradation, changes in the properties of the land (soil, water, vegetation) do not correspond linearly to changes in vegetation biomass dynamics. Depending on grazing intensity and other human or natural induced pressures, such as the degree of aridity, the system’s resilience can be reduced and small changes can lead to transition between stable states with dramatic difference in ecological value.

Albatera, Castelsaraceno, Messara and Randi Forest face various levels of grazing pressure that contributed to the levels of degradation or conservation in discreet plots of each Study Site. Here, estimates of grazing capacity and grazing pressure from each Study Site will be used with a simple grazing model to quantify long term equilibrium states and the effect of annual climate variations on these states.

Fire pressure

Fires are part of the natural ecosystem processes in many regions of the world. The relationship between fire frequency and aridity normally shows a bell-shaped curve. The occurrence of fires is highest in medium environmental stress and decreases when stress both increases (due to a lack of biomass and fuel connectivity) and decreases (higher moisture content of fuels). Particularly in the Southern Mediterranean countries, where the abundance of dry vegetation due to seasonal or out-of-season droughts confers an extreme flammability to the plant communities, it is possible that changes in land use in the Mediterranean by recent socio-economic changes may have affected the timing, magnitude, frequency and intensity of these fires. However natural Mediterranean ecosystems have coevolved with fire and are, hence, adapted to it although fire increases the transition rate from forest to shrublands and from shrublands to grasslands. Nevertheless, the frequency of forest fires has increased in the last 50 years and these concentrations of fires in small time scales generate a successional loop with little progression of ecosystems towards mature woodlands or forests.

The impacts of fire on ecosystem services depend on many factors and any attempt to reduce fire risk and its impacts through good land management practices requires a good understanding of how fire affects the structure and functioning of ecosystems. Vegetation composition and predominant regeneration strategies after disturbances (e.g. seeders or resprouters) will primarily control the retention of resources in situ by determining the start and rate of soil protection and, hence, soil erosion rate. However, the risk of off-site damages by runoff and sediment export is significantly increased after forest fires although it might be site-dependent. The loss of soil resources greatly depends on fire intensity. Fires that generate high soil surface temperatures produce combustion of soil surface organic matter and nitrogen, as well as soil sterilization and sealing.

Socioeconomic pressure

Environmental degradation can only be understood within the context of the society that the environment supports. Therefore, the incorporation of socioeconomic variables may improve our understanding of the human causes of land use and ecosystem change and stimulate the creation of relationships among them; information on these variables will support the development of people's motivation and interest to identify and resolve social issues as well as to forecast trends in local policy and economic development. Trends in demographic features such as the urbanization, aging and education level as well as land use and land use intensity changes are often connected to and feedback on the deterioration of what is perceived as the desirable ecological status and ecosystem services. Traditionally, studies across Europe certify that growth in population leads to growth in agricultural production which may also apply to demand or profit opportunity related to expansive pastoralism and grazing. Nevertheless, this relationship may not hold across time scales and regions, due to changes in technology and use of inputs in agricultural production. The direct connection of socioeconomic variables to environmental changes is a difficult task, especially at small spatial scales because of the importance of other variables that affect demand or create spatial impact variation such as global market trends.

Furthermore, socioeconomic feature analysis can often lead to contradictory results. For example, the parameter of poverty is considered to aggravate the resource overuse in developing countries and possibly in the Mediterranean of the current financial crisis. The "poverty trap" or "downward spiral" theory suggests that those not able to invest in resource conserving practices continue to exploit hillsides and overgraze land instead, as they cannot wait for rangelands to recover. Similar "inappropriate" management of natural resources under the forced condition of poverty leads to a general land "mistreatment" thus causing negative feedbacks on poverty. However, this hypothesis disregards the fact that poor communities implement land use controls to stabilize their income through increased vegetation cover and that poor policy or/and policy implementation can be a more important hurdle against escaping the poverty trap. Apart from financial resources, educated farmers are more likely to adopt new technologies and numerous studies show that farmers with education have more benefits from their land and generally higher incomes. Also, higher education may provide off-farm labour opportunities, which can intricately link with agricultural practices.

In the case of wildfires, demographic and socioeconomic factors have been studied less, but they also affect fire occurrence, as changes in behaviour and new lifestyles are the main factors driving the spatial distribution of people in forest areas. According to literature, three main variables correlate well with fire events: population density, wildland-urban interface (WUI) and landscape accessibility. A power law relation between population density and fire probability has been found in Japan while found fire frequency was well modelled in California (USA) by factors such as population density and distance to the wildland–urban interface. Similar results, have been found identifying WUI as a statistically significant wildfire risk factor. Finally, researchers in a number of Mediterranean regions have concluded that spatial patterns of ignition are strongly associated with landscape accessibility. In particular, contrast values highlight the importance of distance to roads, recreational areas and trails as an important predictor of ignition risk. These patterns have also been encountered in previous studies.

Several studies relate socioeconomic factors to fire occurrence regarding developed countries, characterized by a higher level of industrialization and quality of life (e.g. low poverty, high educational level, adequate housing conditions). In Northern Mediterranean countries, the decrease in rural population and land abandonment since the mid-20th century have significantly determined the quantity, quality and structure of biomass (fuel) that confer a very high risk of fire for the ecosystem. Post-fire regeneration patterns of these landscapes is clearly driven by human activities through fire ignitions and previous land use. The increase of recreation versus agricultural activities and the urbanization in forest areas may indicate a potential shift in the nature of Mediterranean wildfire risk. Nevertheless, associations detected between socioeconomic conditions and fire occurrence have been found to exist with contrasting demographic characteristics in developing countries. Other contradictory findings include that of lower unemployment correlating with higher fire occurrence, fire generated opportunities of a job for firefighters, expression of social dissatisfaction through arson.  

References

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