2. Effects of Climate Change on Agriculture in the Mediterranean Region
Mediterranean climatic is very similar to any of the following regions across the globe: California (United States); Central Chile; Cape Region (South Africa); and the southernmost regions (Australia) [called Mediterranean climatic regions (MCRs)]. The five regions constitute 2% of the Earth’s surface area, 20% of the world’s plant species, and 5% of the world’s population. However, just 6% of land in California is utilized for agriculture, whereas 37% of land in Australia and 55% in Chile’s central valley are used for agriculture
[40][5]. Climate change increases the likelihood of drought and high heat, which is detrimental to agriculture in MCRs
[41][6]. In semiarid regions, variable water supplies make it difficult to cultivate crops and have substantial social and economic consequences
[42][7]. To make MCR less susceptible to CC, adjustments must be made to crops (such as annual crops, vegetables, orchards, and vineyards), cropping systems (the sequence of crops and management strategies employed on a particular farm area), and farming systems. Adaptation is altering the environment and its present or anticipated consequences to mitigate or prevent adverse effects and take advantage of positive ones. Numerous technical methods assist crops and agricultural systems to adapt to climate change. A deep understanding of the role of technology in adaptation requires the examination of how technology is used for extension and training
[43][8]. Many rainfalls characterize MCRs in a short time during the year. Furthermore, rainfall in MCRs changes a lot from year to year and from month to month as a result of climate oscillations
[44][9]. In addition to the above characteristics, the temperatures have gone up and rainfall has gone down in MCRs over the past 100 years due to CC
[45][10]. The prediction models of MCRs by the end of the 21st century have shown that MCRs will have even less rain and warmer temperatures
[46][11]. Another study suggested that rain is less often in the winter in MCRs, but in some places, it would rain more heavily
[42][7]. Changes in how much and where it rains, along with high evaporation and transpiration (loss of water vapor through the stomata of plants) in the spring and summer, will cause the MCRs to lose more water over time. Hence, the effect of water and temperature on agriculture will be discussed in the next two sub-sections.
2.1. Effects of Water
Drought stress significantly impacts agricultural productivity
[47][12]. Annual crops, such as cereals, are susceptible to progressive water scarcity during the blossoming and grain-filling phases in rainfed parts of the MCRs and semi-arid tropics, resulting in “terminal drought stress”
[48][13]. During certain phenological times, a lack of water hinders leaf photosynthesis. The creation of photosynthetic was carried directly to the grain
[49][14]. Consequently, the number of grains per spike/pod and grain weight is lowered significantly, resulting in lower grain yields
[50][15]. The harvest index, or the proportion of aboveground biomass allocated to grain, decreases during terminal drought circumstances
[51][16]. Photosynthesis provides activities to restore reserves during pre- and/or post-anthesis stages
[41,52][6][17]. As a result, when leaf photosynthetic activity diminishes under terminal drought stress, the contribution of stem reserves (mostly water-soluble carbohydrates; WSCs) to grain is critical
[48][13].
The quantity of water available for irrigation in most irrigated MCRs is decreasing due to recurring drought and intense competition for water resources among agriculture, industry, and urban areas. Higher temperatures, on the other hand, increase evapotranspiration and agricultural irrigation needs
[53][18]. As a result, the objective is to reduce irrigation water use and its negative influence on seed/fruit yield and quality. It is well known that the influence of water scarcity on seed/fruit yield and quality varies greatly depending on the crop development stage. Water scarcity impacts the reproductive and seed/fruit development phases more than the vegetative or maturity stages. Water scarcity during the silking-pollination and blister periods of maize, for example, reduces seed set. It enhances grain abortion, leading to significant output losses
[54][19]. In general, water shortages throughout the blooming and fruit development periods result in a more significant decline in fruit yield than shortfalls towards fruit maturity
[55][20].
2.2. Effect of Temperature
MCR temperatures are anticipated to climb by 2–4 °C by the mid-twenty-first century
[56][21]. High temperatures can affect various physiological and metabolic processes in plants, affecting their development, growth, and production. Higher temperatures related to CC have been shown to impair agricultural output and quality
[57][22]. Even mild temperature increases hasten plant growth, shortening the growing season and decreasing plant biomass. Consequently, changes in phenological dates will change the crop season duration and water requirements. Temperatures and evaporation-spiration will rise in areas with warm spring and summer seasons (severe scenario, up to 4 °C)
[58][23]. Warmer weather (moderate scenario, up to 2 °C) may benefit agricultural production when temperature restricts the duration of the growing season
[33][24].
3. Sustainability and the Five Domains
The climate change in the Mediterranean Basin rates may outperform world trends for most variables, including rising temperatures, rainfall, and desertification, with annual mean temperatures currently 1.4 °C above levels from the late nineteenth century. Since 1950, it has been proven that heat waves and severe droughts have increased in frequency
[21][25]. There is evidence that growing salinity variations may impact regional changes in river discharge along the Mediterranean coastlines, leading to a substantial land shift in the basin’s eastern regions. Even though Mediterranean circulation patterns can be altered, global sea-level rise will dominate future Mediterranean Sea-level change
[59][26]. This pattern might result in local height fluctuations of up to 10 cm. Along the Mediterranean coast, increased CO
2 absorption by the seas and acidification of 0.15 to 0.41 pH units
[60][27] are anticipated to induce significant impacts.
Aside from these changes, the consequences of CC on people could affect infrastructure and ecosystems. Between 1960 and 2015, the population of Middle Eastern and North African (MENA) countries doubled, while urbanization increased from 35% to 64%.
[18][28]. Due to the possibility of substantial yield gains in many southern and eastern land systems, agricultural land management is increasing, primarily via more excellent irrigation, with ramifications for water resources, biodiversity, and landscape functioning. Despite local advancements in wastewater treatment, air and water pollution continue to grow due to urbanization, traffic, and other factors. Political conflicts have a substantial environmental effect, and migratory pressure continues to affect economies with limited resources, making it more difficult for them to adapt to environmental changes
[61][29].
Environmental, human health, human security, and food security are interconnected aspects of CC. The combination has foreseen the possibility of posing a threat and has taken precautions accordingly. Given the lack of resources, the exposure to all possible dangers is unlikely to be comparable to their overall exposure to any of them individually. The combination, on the other hand, may amplify the intensity impact that induces more frequent and consecutive episodes of stress, thereby worsening the countries’ situation. The five interconnected five domains are discussed in the following sub-topics.
3.1. Water Resources
In the basin’s southern and eastern regions, the nations of the Mediterranean experience severe water shortages. Mediterranean countries have to deal with the difficulty of satisfying rising water needs while having a limited freshwater supply. For every two Celsius of warming and the length of dry spells and droughts, fresh water is expected to go down by 2–15%
[33][24]. Generally, the rivers will flow less, especially in the south and east, where water is in very short supply
[62][30]. Most likely, the water in lakes and reservoirs will go down. Stream flow patterns are likely to change, with high spring flows from melting snow ending earlier, summer low flows getting more robust, and winter flows getting more significant and unpredictable
[63][31]. In the future, the amount of water per person in the Mediterranean, which is already very low, will drop to less than 500 m
3 per year. To make sure that aquatic ecosystems work well, it is crucial to meet environmental flow requirements. This outcome means that specific amounts of water will have to be kept in these systems, making them even harder for people to use
[64][32].
Regularly, the coastal parts of the Mediterranean are impacted by flash floods induced by brief, intense rainfall in small catchments
[36][33]. Extreme rainfall events will increase the likelihood of flooding, exacerbated by CC and non-climatic variables such as increased urbanization and inadequate stormwater management systems. Flooding is expected to become more common in many sections of the Mediterranean Basin due to inadequately designed stormwater management systems, impermeable urban surfaces, and people living in flood-prone places
[36][33].
3.2. Managed Ecosystems
The Mediterranean Basin’s forest, wetland, coastal, and marine ecosystems are affected by seasonal fluctuation in the mean temperature and precipitation
[56][21]. The diversity and long-term viability of Mediterranean land ecosystems may be most jeopardized by increased aridity brought on by decreased precipitation and rising temperatures
[65][34]. Greater fire danger, longer fire seasons, and more catastrophic wildfires are predicted due to changing climate, increased heat waves, dryness, and land use
[18][28]. Water levels are also decreasing, and the water quality is deteriorating, significantly impacting freshwater ecosystems
[66][35]. Urbanization, agricultural abandonment, biological invasions, pollution, and overexploitation impact the structure and function of species, populations, communities and terrestrial ecosystems in the area
[67][36]. As a result, the benefits and services of the Mediterranean may be at risk. The changes can be explored in many fields including renewable natural resources (such as food, medicine, and wood), environmental services (such as conservation of biodiversity, soils, and water, regulation of air quality and climate, and carbon storage), and social services (such as recreational, educational, and leisure opportunities, and traditional cultural values)
[68][37].
3.3. Food Production and Security
Agriculture and fisheries are changing Mediterranean food production in social, economic, and ecological ways
[69][38]. As the world’s population grows and diets change, so will the need for food, agricultural products, fish, and animal products. Crop illnesses, yield reductions, and more significant production variability may all occur due to extreme weather events like heat waves, cold snaps, or heavy rainfall during critical phenological stages. Many winter and spring crops, particularly in the southern Mediterranean, are expected to be affected by CC
[70][39].
Olive production will be harmed due to rising irrigation demands due to CC
[71][40]. Local and regional discrepancies will arise, while the influence on aggregate production is not anticipated to be significant
[72][41]. It is anticipated that the phenological cycle of grapevines would shift toward shorter length and earlier blooming, accompanied by increased vulnerability to severe events and water stress
[73][42]. These circumstances may also affect the quality of grapes. Flowering and chilling accumulation are also anticipated to influence fruit tree output
[74][43]. Reduced water, such as in tomatoes, will be the primary factor restricting crop yields
[75][44]. However, water-saving measures might be devised to enhance crops’ quality and nutritional value while maintaining appropriate output levels
[76][45]. Due to CO
2-fertilization effects, yield improvements may occur in some crops, which might boost water usage efficiency and biomass output, even though the intricate interactions among the numerous components and the present knowledge gaps suggest significant uncertainty
[77][46]. In addition, these yields are anticipated to decline in quality (e.g., a fall in the protein content of cereals)
[78][47]. In some regions, sea-level rise and ground subsidence may severely diminish agricultural land. The consequences of sea-level rise will impose more restrictions on agricultural land, notably in the Nile Delta and other productive delta regions
[79][48].
3.4. Human Health
Heat, cold, drought, and storms (direct factors) as well as food quality, food availability, pollution, and the affect CC has on social and cultural issues, and the subsequent impact on human health, are all substantial. The degree and timing of the relevant effects vary according to the local environmental circumstances and the population’s susceptibility
[18][28]. Along the Mediterranean Basin’s coastlines and in heavily populated metropolitan areas, there are locations with particularly considerable variations in ambient temperature and significant heatwaves
[80][49].
High ambient temperatures (often coupled with relative humidity) exceed the land’s inherent ability to disperse heat. As a result, heat-related illnesses and deaths are a possibility, with the elderly, youngsters, and people with preexisting or present medical issues being more susceptible
[81][50]. A rise in heatwave severity and frequency, or a shift in seasonality, presents substantial health hazards for vulnerable people, including the poor, those living in inadequate housing, and those with limited access to air conditioning
[82][51].
Temperature-related disease and mortality rates will rise in the Mediterranean region in the coming decades if people do not prepare themselves for CC and public education, while healthcare systems are not up to pace
[83][52]. The health of the elderly in all Mediterranean countries will become more problematic during heat waves as the population’s life expectancy increases. Climate change may affect the spread of vector-borne diseases due to its effects on the life cycles of vector species, pathogenic organisms, and reservoir organisms
[84][53].
3.5. Human Security
As a result of natural disasters, societal unrest, or a combination of the two, people’s safety is at risk
[85][54]. There was an 87% rise in the world’s population between 1970 and 2010; however, the populations in flood plains and cyclone-prone beaches grew by 114% and 198%
[86][55]. More than a third of the inhabitants in the Mediterranean Basin live within walking distance of the sea. As a result of the small tidal range and relatively infrequent storm surges, coastal infrastructure, land use patterns, and human settlements have developed close to mean sea level
[87][56]. Sea-level rise is expected to impact Mediterranean coastal dangers
[88][57] significantly. Wave overtopping is a significant problem in Northern and Southern Mediterranean ports
[87][56]. Morocco, Algeria, Libya, Egypt, Palestine, and Syria are among these countries
[89][58]. With rising sea levels and local ground subsidence, port cities with a population in excess of one million may be at greater risk of catastrophic storm surge flooding
[90][59]. By 2050, half of the 20 cities with the most significant yearly increase in damages will be in the Mediterranean, according to lower sea-level rise scenarios and current adaptation efforts
[91][60]. More than 11% of North African countries’ populations would be displaced if sea levels rose by one meter.
As sea levels rise, saltwater intrusion will become more prevalent in coastal areas. Saline intrusion negatively influences around 30% of Egypt’s irrigated crops
[92][61]. Salt-affected soils are found in 60% of the Northern agricultural area and 20% of the Middle and Southern Delta areas. In order to accommodate Egypt’s rising population, the environment is deteriorating
[93][62]. In addition, there is a risk that environmental stressors, such as drought, would exacerbate social unrest and lead to a mass exodus. Then resources would be few, and attempts to reduce one risk may harm human community resilience or worsen other threats. The Mediterranean Basin has traditionally been unstable due to its cultural, geographic, and economic complexity
[90][59].
Human security in the Mediterranean Basin is in danger due to the increased stress from CC, making the region’s residents more vulnerable and raising their level of anxiety
[94][63]. The vulnerability has also been exacerbated by environmental mismanagement and overexploitation. The primary causes are the depletion of natural resources on land and at sea, desertification in the northern hemisphere, and the resulting food shortages (particularly in the Middle East and North Africa)
[18][28].