The Mediterranean bioclimate is one of the most vulnerable ones to the impacts of climate change, with a projected increase in temperatures, precipitation irregularity and in the frequency and intensity of extreme drought events, heat waves and storms. Therefore, it is essential to increase the resilience of Mediterranean ecosystems against these threats and other impacts associated with them, especially forest fires.
The agrarian intensification that began in the mid-20th century has caused many traditional mosaic landscapes to evolve in two opposite directions:
A) In flat areas, fields were merged, creating increasingly larger and more homogeneous lands with the removal of millions of scattered trees, hedgerows (70% in France between 1962-99 and 50% in Catalonia between 1957-81) and systems combining fruit trees and crops (90% in France between 1945-2000 and 97% in Spain between 1962-99). The resulting landscapes are simplified, with associated environmental problems: loss of biodiversity, soil degradation due to the loss of organic matter and fertility; soil erosion, compaction and drainage problems; mineral and organic contamination of soil and water, etc.
B) In mid-mountain areas, many arable and pasture lands have been abandoned, being occupied by abandoned forest stands. In addition to these "new forests", most of the remaining Mediterranean forests also face the so-called vicious circle of forest abandonment: the prevailing low productivity, limited by water availability and the absence of management for decades, reduces the economic viability of forest management: in non-Cantabrian Spain, the harvesting rate (amount of timber harvested, compared to the increase in growing stock) is only 15%. The resulting forests are increasingly dense and more exposed to stability and health problems, while becoming more vulnerable to climate change related impacts (droughts, fires, storms, pests), reinforcing the vicious circle.
Agroforestry systems and their contribution to climate change adaptation and other ecosystem services
Agroforestry systems are the deliberate combination of woody vegetation (trees and/or shrubs) with agricultural or livestock production to obtain benefits from their interactions. In this project focus on two modalities: silvoarable systems (woody vegetation combined with crops) and silvopastoral systems (woody vegetation combined with pastoral production). The woody component of the system can be arranged on the field margins (hedgerows), as trees in rows (alley cropping), on islands or scattered, being able to serve multiple objectives simultaneously: production (timber, fruit, mushrooms, forage), protection (biodiversity, soil, water, animal welfare) and landscape. Some of the main benefits provided by agroforestry systems compared to conventional ones are:
[A] Higher ecological resilience and biodiversity, thanks to the increase in number and to the diversification of system components, the creation of ecotones and the restoration of food chains and nutrient cycles. Three associated benefits are: higher availability of auxiliary fauna (making it possible to reduce the cost of pests and diseases control), the reduction of soil erosion and the protection of the physical and chemical quality of water (filtering of agricultural and livestock leachate).
[B] Higher productivity and profitability: these systems are an eco-intensification practice, where the components of the system (woody vegetation / crops and grass) occupy different vertical strata, increasing the total capacity of the system to use the available resources: light and soil water and nutrients. Moreover, the presence of various components increases the number of months during which there is at least one production in vegetative activity.
Therefore, overall productivity is higher and more stable and so the producer's vulnerability to product price fluctuations is reduced. The diversification and the generation of added-value products allow market differentiation and enables additional sources of income (i.e. carbon farming, emissions offset payments, eco-tourism, etc), as well as the promotion of a circular economy at farm level: use of straw as tree mulch; use of pruning debris as fodder or to increase soil fertility, use of tree biomass for energy production, etc.
[C] Less vulnerability to drought and extreme weather events: the woody component creates a microclimate with buffered temperatures and less wind effect, which is positive for the crop or pasture underneath. Trees promote animal welfare by protecting them from the sun and storms and prolong the vegetative period of grass in summer, which is critical in Mediterranean conditions. The forage supply of the system can be increased and diversified by using trees producing food for livestock (fruits, leaf fodder). In forests, reducing tree density to promote silvopastoralism improves the water balance and the vitality and fruiting of the standing trees, increasing pasture production.
[D] Silvopastoralism lowers forest fire vulnerability, thanks to the reduction of fuel load and continuity linked to the double effect produced by the animals of consumption and crushing of low vegetation.
[E] Increased carbon fixation: adding trees to cropland or grassland allows stabilizing and increasing soil organic carbon (less tilled area, contribution of organic matter – litter, fruits, twigs, thin branches and roots…) and enabling the long-term carbon storage in the timber, a renewable resource with multiple applications.
Due to these benefits, the need to promote agroforestry systems is explicitly mentioned in the main recent European regulations, among which the following stand out: European Green Deal, LULUCF Regulation, Strategy 2050, Bioeconomy, Biodiversity and Forestry Strategies or the Farm to Fork Strategy, among others.