Olive Oil: Challenges in a Changing Environment

Abstract

Olive oil is a liquid fat from a traditional tree crop of the Mediterranean region, obtained by pressing whole olives (the fruit of Olea europaea; family Oleaceae) and then extracting the oil. It has a variety of usage such as cosmetics, cooking, medicine, fuel for traditional lamps and soaps. Olive oil is highly beneficial to life, and it is proven to contain large amounts of antioxidants which are biologically active and of great health benefit. However, due to unmitigated climate change, resulting from rising greenhouse gas emission worldwide and especially in Europe, olive oil production is being challenged. There is a prediction of a 30% drop in olive oil production in the southern region of Spain (Spain is the current highest olive oil producer) by 2100, this would mutilate the production of olive oil and the olive sector. Subject to the continuous rise in temperature, as a result of the deadly heat wave that has been plaguing most of Europe, the majority of the non-irrigated olive tree plantations may become unsuitable to cultivate olives. There is therefore an urgent need to mitigate this negative impact on this highly beneficial Mediterranean diet by employing suitable modeled adaptation.

1. Introduction

The traditional tree crop found in the Mediterranean Basin, olives (fruit of Olea europaea; family Oleaceae), is the source of olive oil, produced basically by pressing the whole olives and extracting the oil, such fruit is as shown in Figure 1 [1]. Olive trees were known to be cultivated in Crete, by the Late Minoan (1500 BC), and possibly as early as the Early Minoan [2]. It is worth noting that olive trees cultivation in Crete became explicitly intense during the post-palatial period, subsequently playing a salient role in the island’s economy, just as it was across the Mediterranean [3]. From the eight millennium BC thenceforward, olive trees have been grown around the Mediterranean basin, in Asia Minor and near Syria. Today, olive oil is extremely abundant in Asia Minor, however, it seems to have spread from Syria to Türkiye, subsequently to Greece and Crete. Eventually with the establishment of Greek colonies in other parts of the Mediterranean, farming of olive was brought to places like Spain from where it has continued to spread all over the Roman Empire [4], however, today, it is popular around the world.

Figure 1.

Olives fruits. Source: [1].

It is of great interest to know that olive oil is highly rich in fatty acids and functional bioactive compounds like Phospholipids, Carotenoids, Phenolics, and Tocopherols with various biological activities, these contents are responsible for possible potential health benefits of olive oil [5]. They also contribute to the taste and distinct flavor of olive oil. Furthermore, they are known for the remedy of some tropical disorders such as malaria and fever [6]. Olives are seldom utilized in their natural form because of their bitterness, nonetheless, they are ingested either as table olives or oil [5].

Authors have claimed that oleuropein a phytoconstituent in olive, have antibacterial properties, some also assert that oleuropein could act against toxins produced by Staphylococcus aureus and possibly have antiviral effect against hepatitis viruses and herpes. Moreover, there is the proposition of the potential antiviral activity of olive leaf extract against the virus that causes acquired immunodeficiency syndrome [7].

Studies have also shown that polyphenols might inhibit the development and reproduction of Klebsiella pneumonia, Bacillus cereus, Escherichia coli, and Salmonella typhi. Hence, olive oil has been reported to have potential antibacterial properties for respiratory and intestinal infections [8].

However, in spite of the great environment for cultivation of olive oil, one of the greatest challenges of our time is climate change. Impacts from a changing climate will certainly affect the natural world as well as the built environment, thereby giving rise to a new comprehensive approach to adaptation. All resolve towards assessments of environmental impacts, future planning of our cities, built environment, setting standards and codes, identifying risks, are usually carried out based on data and knowledge of the past. However, the future tends to be obviously different, with a changing environment due to challenges faced, from a degrading ecosystem to a severe change in the climate, this will literally force a reconsideration of the knowledge system. In the face of a rapid changing climate, the ability of a system to absorb surprises and disturbances, and for the moment accomplishing a condition of dynamic equilibrium that will permit systems evolve and grow while keeping their coherence is entirely complex global issues.

2. Types of olive oil

Olive oil is of various types: virgin olive oil (edible), extra virgin olive oil (edible), refined olive oil (edible), olive-pomace oils (non-edible) and lampante olive oil (non-edible) [8]. Table 1 highlights the nutritional value of olive oil.

Nutrient	Amount
Total fat	93.7 g
Fatty acids	15.4 g
Stigmasterol	1.02 mg
Campesterol	5.68 mg
Beta-sitosterol	126 mg
Beta-sitostanol	2.55 mg
Delta-5-avenasterol	23.1 mg

Table 1.

The nutritional content of 100 g of olive oil.

Source: [8]

3. Potential properties and benefits of olive oil: uses of olive oil and health benefit

Studies have shown that a phytoconstituent in olive called Oleuropein has antibacterial properties against bacteria, including mycoplasma. Moreover, there is the possibility of the phenolic chemicals in olive oil to break down bacterial membranes, hence showing antibacterial activities. Several researchers also state that oleuropein may act against toxins produced by Staphylococcus aureus and could have an antiviral effect against herpes and hepatitis viruses. Likewise, the potential antiviral activity of olive leaf extract against the virus that causes acquired immunodeficiency syndrome has been proposed [7].

Olive oil has been shown to have potential antibacterial properties for respiratory and intestinal infections [8]. Nevertheless, this needs further confirmation.

Researchers have also found that consuming extra virgin olive oil might reduce liver tissue damage in animal models. Furthermore, the combined therapy of olive oil and camel milk in animal models demonstrated possible liver protective effects in drug-induced liver toxicity due to their potent antioxidant action [8]. However, it is worth noting that diseases such as liver disease can be very challenging and need real diagnosis and treatment by experts.

Some scientists researched on the impact of olive oil on colon cancer. From their investigations they suggested that the presence of antioxidants, fatty acids and phenolic compounds in olive oil might play an important role in reducing the risk of colon cancer [7].

Essentially, there are various properties of olive oil including being a potential antioxidant, having potential anti-inflammatory, anti-microbial, anti-atherogenic, anti-tumor, anti-platelet aggregation activities. Olive oil might help in lowering blood pressure, they might act as an as well as liver-protective immunity enhancer, wound healing, anti-allergic agent. They might also have brain-protective activity.

4. Climate change

The word Climate, indicates the long-term regional or global average of rainfall, humidity, and temperature patterns over seasons, years or decades. Generally, weather could change in just a few hours, on the other hand climate changes over longer timeframes. Climate change is the notable variation of average weather conditions being, for example, drier, wetter, or warmer—over some decades or longer. However, it is the longer-term trend that distinguishes natural weather variability from climate change.

It is worth noting that human activities could lead to atmospheric composition change either directly (through emissions of particles or gases) or indirectly (through atmospheric chemistry). Anthropogenic emissions are drivers of changes in well-mixed greenhouse gases (WMGHG; mainly carbon dioxide, methane, nitrous oxide, and the chlorofluorocarbons) concentrations during the industrial era.

The earth’s climate is changing and the global climate is projected to continue to change over this century and beyond. The extent of climate change surpassing the next few decades will primarily depend on the amount of greenhouse (heat-trapping) gases emitted globally and on the remaining uncertainty in the sensitivity of the Earth’s climate to those emissions [9]. Hence, global annual averaged temperature rise could be limited to 2°C or less, especially with significant reductions in the emissions of greenhouse gases (GHGs). Interestingly, without major depletions in these emissions, the rise in annual average global temperatures, relative to preindustrial times, can possibly reach 5°C or more by the end of this century [9].

Furthermore, there is the continuous rapid changing of the global climate in comparison to the pace of the natural variations in climate that have occurred throughout earth’s history. It has been observed that trends in- sea level rise, globally averaged temperature, upper-ocean heat content, arctic sea ice, depth of seasonal permafrost thaw, land-based ice melt, and other climate variables give consistent evidence of a warming planet [9]. These observations are strong, solid and established by multiple, independent research groups around the world. The Figure 2 below is a representation of global average temperature anomalies; it shows that from the 1880s global average temperature has warmed approximately 1°C.

Figure 2.

Global average temperature anomalies, departure from 1881 to 1910. Source: [9].

The plot in Figure 2 reveals how much global annual average temperatures for the years 1880–2022 have been above or below the 1881–1910 average. Temperatures for years warmer than the early industrial baseline are shown in red; temperatures for years cooler than the baseline are shown in purple.

Many think climate change basically means a condition or situation of warmer temperatures, however, temperature rise is only the beginning of the story. Since the earth is a system, where everything is connected, changes in one area could influence changes in all other areas. Therefore, the following consequences among others on climate change has been revealed; water scarcity, intense droughts, rising sea levels, severe fires, melting polar ice, catastrophic storms, flooding and declining biodiversity.

Above all, climate change can also affect human health as discussed earlier, it can affect housing, safety, work and even ability to grow food. Conditions such as saltwater intrusion and sea-level rise have advanced greatly to the point where we have whole communities relocate, also there is also the risk of famine as a result of protracted droughts.

4.1 Roles of olive trees on climate

In Spain, this current crop occupies 14% of the country’s agricultural area, representing nearly half (45%) of world production (Alonso, 2022). As obtainable with any large plantation of trees, large olive groves areas, absorb a considerable amount of CO₂ [10]. It was estimated that “each olive tree, on average, absorbs 30 kg of CO₂ per year (considering the fact that there are larger and smaller olive trees) this makes the olive grove an important factor in curbing climate change”.

Olive trees can to certain extent mitigate the effects of climate change via their absorption of CO₂, however they are often victims of climate change [10]. It is worth noting that increasing GHG emissions are causing rise in temperatures and in the frequency of dire weather events such as storms, droughts or unseasonal temperatures [11]. Findings from a recent research showed that climate change is expected to cut down on the area where olive growing is possible in Andalusia, being Spain’s largest oil-producing region, as well as other possible olive-growing regions primarily due to hotter and drier weather in autumn and summer [12]. The absence of rain and anticipated dry spells will definitely bring about water stress to the olive tree and, at the same time temperature increase will result in heat stress. This ‘stress’ destroys trees physiologically, compromising flowering and thus olive production [10].

Olive trees have been judged as durable mythologically and historically [1]. Nonetheless, irregular seasonal changes as well as temperature increases are affecting crucial processes that result in a good season. Olive flowering is the most phenological process affected by climate in the olive orchard, this usually occurs in the season of spring, its onset is extremely susceptible to temperature as well as to the period where olive fruit mature and ripens, during mid to late summer. It’s been observed in recent years, the advancement of flowering and the acceleration of ripening, this usually causes the flowers to drop before they are set into fruits. Moreover, there has been a decline in the number of olives per tree as well as change in the quality of these olives oil. Furthermore, the risk of phenological stress due lack of water resources and high temperatures in summer is on the increase. All the above mentioned factors gear towards less productive harvests [1, 13].

Some researchers at the Consejo Superior de Investigaciones Científicas (CSIC), built a biophysical model called OliveCan 2.0 by virtue of the challenge of making dependable forecasts on the response of olive groves to climate change, this model simulates a number of the processes that may occur as a result of the effects of climate change. The model reveals, for instance, the reduction in flowering percentage in a scenario of elevated temperatures or the propensity of flowering dates to proceed in weeks or months in this same scenario with higher temperatures [1].

Another group of researchers who happen to come from the University of Cordoba in Spain and the Research Center for Geo-Space Science (CICGE) in Portugal, predicted likely changes in the contemporary distribution of diverse olive tree varieties. Two varieties, presently constitute 80% of the whole Andalusian olive crops: hojiblanca (20%) and picual (60%), being the most versatile and productive. Nevertheless, for centuries olive producers have chosen some other varieties more adapted to difficult terrain, soil types, or to certain local climates [14].

Furthermore, it’s been discovered that these local varieties are at more risk of disappearing. According to Arenas-Castro, those local varieties have specified needs that are spatially restricted since the varieties are themselves more restricted an example he cites is nevadillo, a variety presently cultivated in Sierra Morena, near Cordoba. The precise climatic conditions to cultivate it would have completely vanished by 2100 [14].

However, other experts are not exactly sure of the fate of these trees under climate change, for instance, Diego Barranco, an olive cultivation and olive genetics expert at the University of Cordoba, expressed that olive trees are unlikely to die off just like that because they are extremely hardy. He reiterated that such dire climate changes are not anticipated in the medium term.

Nonetheless, growers most likely will substitute struggling varieties with more adaptable ones. Barranco predicts that these changes are bound to be slow-paced, thereby making it unlikely that any variety is completely lost [14].

4.2 Effect of climate change on olive tree

Spain has been said to be the largest producer and exporter of olive oil in the world, even ahead of Greece and Italy [15]. Climate change has adversely affected the world over the years. Of the most recent impact is that on the production of olive oil in Europe. It is worth noting that olive groves have actually emerged with the Mediterranean climate and are famous for their resistance to water scarcity. There has been an incessant plaguing by this deadly heat wave which has resulted to a direct reduction in olive oil production in most of Europe such as in Italy and Spain.

Besides, recent years have evidenced that even the olive tree, a symbolically resilient tree, may perhaps be one of the crops grievously affected by the effects of climate change, endangering a millennia-old source of culture, subsistence and commerce [13].

Such as been observed with olive trees submerged in floodwater (Figure 3). Extreme weather events and shifting climate patterns have caused tremendous heavy rainfall in olive-producing regions. As olive trees are adapted for dry soil conditions, this can cause crop failure and root-rot.

Figure 3.

Olive trees submerged in floodwater. Source: [1].

4.3 Effects of climate change on olive oil industry

Some researchers from the CICGE in Portugal and the University of Cordoba in Spain tried to investigate how well the olive industry will adapt to the effects of climate change. They discovered that warmer winters and increased drought will reduce the number of land available to cultivate commercially relevant olive varieties, reducing production by 30% before the end of the century [16].

It is worth noting that the climate of Andalusian favors olive trees cultivation. They are resistant to drought and heat, these are common during summers. The winters, however, are cold, though temperatures rarely drop below −8°C, the tree’s lower tolerance limit. In the case of flowering olive trees also need a bit of a chill during winter in order to flower during spring, a physiological necessity known as vernalization.

In order to evaluate the response of current olive plantations to climate change, the species distribution modeling (SDM), an algorithm-based computer method was used by the researchers. This tool is often used to forecast what areas are adequate for the presence of a particular species based on environmental features. Hence, they could predict the future evolution of the most common olive varieties by combining high-resolution climate projections with SDM and extremely detailed satellite imagery.

However, [16], reported that “being the first time this method was developed, the model was detailed and tailored to specified olive varieties that were cultivated commercially”. They could correlate each tree’s specific location with its predicted levels of temperature, precipitation, evaporation, and so on.

The researchers discovered that the most salient factor that will reduce olive production is reduction in rainfall and loss of soil humidity. It was predicted that five of eight Andalusian provinces were to lose olive production, with decreases in fit land for olive production of 25% in Cadiz, 29% in Seville, and a lesser proportion in other regions. They also realized that some mountain areas will become better suited for cultivating olive trees, as these normally colder regions will become more temperate. Nevertheless, these areas are, for the most part, natural reserves or presently occupied by other crops.

5. Possible adaptations

A period of agricultural and, therefore, social change and uncertainty could lie ahead. There is the need to work, adapt and protect landscapes that are as dear as they are tied to our Mediterranean past and present.

Adaptations exist for both short and long term scenarios, for the short term scenario, there is an increased possibility of crop failure, while looking at the long term effect, the risk is expressed in an overall reduction in yield quality and quantity [10]. Going by the OliveCan 2.0 projection wherein flowering take place earlier in the year when the weather is warmer, growers can adapt in the short term by altering their patterns of cropping. Large investments is required in irrigation as well as in the adjustment of the times of the year of its application in order to prevent water stress [17]. However, there could be situations that might not be so easy to adapt to. For instance there was a small localized tornado in Mallorca in the year 2020, which wiped about 80% of the oil crop on the island of the largest producer of this oil crop.

Extreme weather events like these—more frequent cold or heat waves, new suboptimal average growing temperatures, and acute and unforeseen pest outbreaks will require utmost transitions in olive farming. In order to get by with these changes, it will be expedient to investigate the most robust and resilient olive varieties, conserve soil health to maintain or improve water retention, consider intercropping techniques, in which different species are grown at the same time on the same area of land, and, in some instances, even shift the area of olive orchards to more conducive areas altogether [1]. As a result of the latter, it could be argued that, as areas in California, New Zealand or central Europe can conveniently accommodate olive groves, the competitiveness of the Mediterranean coastal strips will decline, and with it Spain’s leading status in global olive oil production [1].

6. Conclusion

Olive oil production is currently being challenged due to unmitigated climate change, resulting from rising GHG emission worldwide and especially in Europe. Although, researchers have observed that as obtainable with any large plantation of trees, large olive groves areas, absorb a considerable amount of CO₂, with the emphasis that, it has been estimated that “each olive tree, on average, absorbs 30 kg of CO₂ per year (considering the fact that there are larger and smaller olive trees) this makes the olive grove an important factor in curbing climate change”. Despite this postulation, the overall effect of climate change on olive tree and olive industry is still overwhelming despite adaptive measures.

Hence the urgent need to mitigate this negative impact on this highly beneficial Mediterranean diet is needful via the employment of suitable modeled adaptation such as changing cropping patterns, irrigation etc. It will also be expedient to investigate the most robust and resilient olive varieties, conserve soil health to maintain or improve water retention, consider intercropping techniques, in which different species are grown at the same time on the same area of land, and, in some instances, even shift the area of olive orchards to more conducive areas altogether. These measures may therefore anticipate the effects of climate change on olive crops and provide early estimates of fruit production, at local and regional scales, as well as forming the basis of adaptation strategies.

Acknowledgments

I would like to acknowledge the staff and students of the department of Biological Sciences, Ajayi Crowther University, Oyo, Oyo State, Nigeria.

Conflict of interest

The authors declare no conflict of interest.