Record-breaking droughts, fruit flies that survive unusually mild winters to ravage in the spring, and pathogen outbreaks, like the one in Puglia that has claimed more than a million olive trees.
It might seem like climate change could spell the end of the olive oil world, but not so fast, says Luigi Ponti, a research scientist at Italy’s National Agency for New Technologies, Energy and Sustainable Economic Development.
His research on the effect of warmer temperatures on the olive sector has been published in scientific journals and provides a valuable framework for continued studies on this important topic. And like so many complicated issues, when we ask, what will climate change mean to olive oil producers around the world? The short answer is: well, that depends.
They’ve been looking better over the course of the time at this and our knowledge have improved. If I had to pick the key issue for ecosystems, because agricultural fields are ecosystems in the end, nothing less and nothing more, I think that the key issue here is complexity. When studying ecosystems in general and agriculture ecosystems in particular, the main barrier to understand them, that means the main barrier to manage them, is complexity.
Climate change is just another additional level of complexity that is on top of the rest of the biological and physical layers that you have. It makes it harder to manage them because you have certain assumptions based on which you try to manage an olive field for example, an olive grove. Those assumptions are challenged by this change. It was very to the point in your introduction when you said that it depends what the effects are.
This is what we have attempted in the study your referred at the beginning of the interview. There’s a bunch of species that we call biodiversity, that interact to each other and with the climate. Each of them have different requirements for growing and developing, reproducing, and the climate affects the way they survive or die. It’s a set of non-linear interactions that it’s difficult to project in the future.
Acquisition of resources and allocation of those, it would be food or organic matter or for a plant it would be acquiring the light from the sun, then you have to allocate those resources and you do it the same way with the same priorities regardless of the kind of organism you are on this planet. This simplifies, computationally it’s easier to describe the organisms that way. Also it tells you what’s going on by ecological analogy, you kind of know what’s going on in the underlying dynamics. It helps you understand the interactions and the processes that are occurring in the field.
I wouldn’t be able to tell you without making the analysis what would be the outcome of the interaction of the two, of the plant and the fly, as the climate warms because that entails looking at what happens on a daily basis and season after season because that depends of course, as you said in the beginning, on the fact that the fly survives better or it doesn’t survive from one season to the next over the Summer. That’s a matter of the daily patterns of weather and how it interacts with the plant. That’s why the model is there, because you kind of have an idea of the tolerance to change in temperature of the plant and of the fly, but to get an answer of the trend over an extended period of time based on the daily pattern of weather, you need an analysis tool that reproduces sufficiently well the biology.
Then the patterns that came out were not entirely surprising because as biologist, I’m an agronomist, I know that when the weather is very hot in the Summer, I know it’s basically the same as you were treating with an insecticide against the fly. It has the same effect, it kills most of the population of the adult flies. We know that, to see that the fly is not doing good in the southern part of the Mediterranean basin prospectively if the climate warms, it was not surprising.
You see that, in the study, when we look prospectively at the changes in yield, that there are regions in the southern Mediterranean basin where you have actually decreased yields. That’s because in those places you reach a point where the cost, that is basically a cost that the plant sustains because of respiration as the temperature warms the respiration, the metabolic cost for sustaining the metabolism of the plant increases and it cannot be compensated by the increase in the organic matter, dry matter, that is being synthesized, so there is a threshold for the tree too.
When it’s too hot it’s not going to be able to increase further the yield. Even if you add irrigation, that’s not going to change it. This is an important consideration in a climate change scenario because the pattern of precipitation or the fact that you get irrigation water will not affect the temperature constraints because at a certain level respiration will be too costly and even a plant like olive, which is drought resistant, it’s taken as probably the model of drought resistant plant in arid climates, at a certain point will close stomata.
The plant for synthesizing yield needs to exchange gases with the atmosphere. It needs to get CO2 and to use the energy of light to produce photosynthates that go to the fruit. That will last until it’s too hot. The plant to prevent desiccation, not to die, it has to close the stomata, which is the little holes on the leaves through which the gases exchange occurs. After that point not photosynthesis is possible. There are limits, physiological limits for the plant when climate warms.
They used a seven year period of yield records and they put it georeferenced, it means that on a grid that I think was five kilometers or so, they tell you what fraction of the land is covered by olive and what’s the average yield. In that number you get embedded all the things that I said before, planting density, the way the cultural practices and varieties. We use that as a basis that we scaled with the projections that we got running the model in the future with the climate change scenario. That way we try to overcome this limitation.
Sure it is true that there’s a lot of variability on the ground, that it’s impossible to reproduce. If you want to get an answer on a trend in the future, one of the ways you go about that is using what’s present right now and then you scale it with the physiological response of the plant and the fly in the future. That way you get an answer that is valid across the Mediterranean basin. In terms of the drier summers that you mentioned, what we assumed is that the changes in temperature and the limitations that this change will exert on yield will not be cancelled by having additional irrigation water as I told you before, because no matter how much water you have, you reach a point where the plant cannot produce more yield just by the fact that you have more water, because it’s a matter of the temperature increase.
These are the kind of problem that may occur. This is also the reason why in Europe especially we have common agricultural policy that sustains those kind of farmers that are in marginal environments and implements ecologically friendly ways of practicing agriculture. We pay farmers for the services that they provide to the rest of the community because we know that the margins in terms of the market are low, but we know they’re very important environmentally and ecologically.
I know you worry about the cultural impact and the loss of a way of life if that happens because I previewed a chapter you wrote for a soon to be published book titled “Bio-cultural diversity in Europe.” Your chapter title is “Preserving the Mediterranean diet through holistic strategies for the conservation of traditional farming systems.” There you wrote, “The challenge in small to large farm is to reinstate social organization and collective strategies in farmer communities that make full use of holistic knowledge about food systems.” What are some example of changes you might see communities adopt armed with data from the analyses you and your team are conduction?
There’s not a price tag on that, only by collective action you can move toward that direction. It’s not only my study that indicated that direction, there’s a lot of evidence showing that. For example for olive, a lot of what’s going on ecologically, even in the more intensive agricultural fields like the market rewarding crops, depends on the biodiversity that surrounds it, even below ground. Which means that the land that is managed less intensively, like it would be olive groves or the agroforestry systems that are abundant in the southern Mediterranean basin that I mentioned in my chapter, that resembles savannas. The below ground diversity, at the microbial level, they exert functions that are vital to maintain the functionality of the more productive land that is embedded in the same landscape.
The evidence is growing of that and we need to realize that. We need to pinpoint that in order for the diversity of the landscape to survive, because then the market value you get it from the cash crop but you know you can get that yield because it’s embedded in an agricultural landscape that features different elements. Many of these elements are not rewarding in terms of the market but are vital in terms of the functionality of the ecosystem. One of these elements is probably olive, there is one thing that I say in the paper, that has been shown in a couple of papers, that below ground biodiversity is as important as the above ground biodiversity in terms of the productivity and maintaining the productivity and increasing the resilience of ecosystems and entire landscape to climate change.
One thing that is important to keep in mind is that when we think of agriculture and climate change, we think of landscapes. We have to think or relationships between the above ground and below ground biodiversity, that they interact using the plant as a connector. When you want to do something useful in term of the climate change, especially that is useful for farmers, you have to build in resiliency in the system and you do that by increasing also the below ground biodiversity, then of course by diversifying the landscape, and then of course by keeping in the landscape key elements like traditional perennial farming systems like olive for example in the Mediterranean. Which is even isolated trees or small groves still resist throughout the Mediterranean.
It’s like a fabric that unites all the landscape of the Mediterranean and has probably an ecological function that we still have to uncover, but the first evidence is coming up and it’s clear what is the pattern. Olive grove systems in the Mediterranean basin were developed over the course of centuries in an interaction of people, the land system and the climate to resist a certain kind of pattern that has probably already learned to deal with drought in the past because that’s embedded in the Mediterranean climate. It rains very sparsely and every couple of year probably if you’re lucky.
They’re already doing that in the field, what they did, they made something that is very ecologically sensible. If you look at the ecological literature you see that to build a sustainable agricultural system you need to reproduce certain elements of the natural vegetation. Usually your first and better bet would be to look at the primary natural vegetation, the secondary natural vegetation which is what regrows after you cut down the primary forest, which probably in the Mediterranean doesn’t exist anymore unless you go to some remote place. But it’s very rare to encounter the primitive vegetation that was here. It’s a landscape and a region that has experienced very deep interaction with the human system.
The olive tree, you also find in the secondary forest in the Mediterranean basin. It’s a natural system if you look at it closely, because it’s what you find also in the forest that is next to the cultivated field in the end. It makes ecological sense to have it there. The kind of fertility that develops in the soil after centuries of having olive groves there, it’s very different than if you plant an olive tree today.
It’s kind of well conserved across the Mediterranean basin. If we don’t make any effort to conserve what’s still there in terms of cultural practices and traditional knowledge and the way people farm the land and traditional varieties and the landscape, and the way we maintain the lands in the form it is right now, it would be a waste of time to just promote the Mediterranean diet simply as a set of recipes that we find in a book and we try to make ourself in our kitchen. Because UNESCO said that already, when describing what the Mediterranean diet is. The agricultural part is embedded.
Yes it’s embedded but it’s disappearing and we have to make efforts to conserve that. That’s why I mentioned in the chapter a very important FAO initiative that is called Globally Globally Important Agricultural Heritage systems (GIAHS). That is sort of what UNESCO does but agriculturally. They try to select across the world agricultural systems that are run by local people that are irreproducible, which means that if they go away it will take another say one thousand years to redevelop the level of knowledge and management that they currently have. This is at least partly too for olive groves in the Mediterranean basin, I think.