Programma della conferenza

This speech serves as an introductory contribution to the discussions on the "Effects of Climate Change on Ecosystems" session. Ecosystems are communities of living things, including plants, animals, and microorganisms, interacting with each other and the physical world. People rely on ecosystems for many benefits, such as food, water, clean air, building materials, and recreation. Ecosystems can vary in size, from large ones (areas surrounding a national park) to as small as a single fallen tree. They can also overlap with one another or be part of larger ecosystems. These connections between ecosystems make them dependent on one another, and not dependent on the organisms within them. Climate change affects ecosystems in many ways. Climate controls how plants grow, how animals behave, which organisms thrive, and how they interact with the physical environment. The IPCC warns that if current warming trends continue, global temperatures could double by 2030-2052, causing devastating effects on ecosystems worldwide. The ocean, which absorbs over 80% of global warming, is particularly affected. Elevated sea-surface temperatures are damaging coral reefs, leading to bleaching and extinction. Ocean acidification, caused by higher CO2 levels, further threatens corals and shelled sea creatures. Sea levels are rising due to ocean water warming and the melting of land-based glaciers. Over the last century, the sea level has increased by an average of 20 centimeters. All regions at the global level are experiencing the impacts of climate change, but impacts vary by area and ecosystem. People are taking many actions to help ecosystems adapt to climate change impacts or minimize the effects. For example, environmental agencies that manage the nations' natural resources are now considering climate change in policies and planning. At the local level, many groups are preserving habitats and restoring ecosystems that have been damaged or disturbed in the past.

Agricultural food security is threatened by climate change impacts, which can distress crop growth and favor the spread of infectious diseases. We examinethe synergism of two potential causes of future yield failure in peach production: the effects of global climate change on fruit tree blooming and on the spread of fungal diseases.
The ‘disease triangle’, well-known concept in plant pathology that represents the interplay between the environment, plant hosts, and pathogens, was evaluated for brown rot in peach orchards in light of climate change. Coupling a climate-driven mechanistic phenological and epidemiological model across the French continental territory, we provided projections of yield losses for four peach cultivars (early, mid-early, mid-late, and late) in the XXI century under different climate change scenarios. We considered as adaptation strategy the possibility of shifting peach production sites to new suitable areas.
Global warming is expected to impair fruit phenology with blooming failure events in the south-western part of the country that comprise the 31% of the French territory at the end of the XXI century. This will be less extreme under the more moderate greenhouse gas (GHG) emission scenario, even though sporadic blooming failures will still occur that will involve less than the 10% of the French territory. In contrast, future warmer and drier conditions will decrease brown rot-induced yield loss in the historicallocations devoted to peach cultivation. Thanks to the considered adaptation strategy, the peach national yield could still be fulfilled even under the most extreme GHG emission scenario. Comprehensive mathematical frameworks, that concomitantly consider the climatic effects on the plant hosts and on their pathogens, are required to provide reliable future predictions of crop yields and to inform control and adaptation strategies to guarantee food security under global warming.

Oceans are critical for sustaining life on Earth, acting as carbon sinks, regulating climate, and providing essential ecosystem services for human wellbeing. Net Primary Production (NPP), defined as the rate at which phytoplankton convert inorganic carbon into organic matter via photosynthesis, represents the primary process sustaining the flow of energy into ecosystems. Consequently, from a theoretical point of view, NPP may also represent the most important driver influencing species richness and abundance. This study represents a proof of concept of the intricate relationship between NPP and biodiversity in marine ecosystems on a global scale, utilizing data from satellite observations and in-situ measurements. Results indicate a strong linear correlation between NPP and biodiversity, suggesting that higher productivity supports greater species richness and ecosystem resilience. Moreover, our findings highlight that diverse marine ecosystems tend to be more productive due to factors such as complementarity and functional redundancy among species. However, this relationship is complex, with some highly diverse ecosystems potentially experiencing reduced productivity due to competition for resources. Current trends in global environmental changes, including global warming and eutrophication, are likely to alter this balance. Warming sea temperatures, changes in ocean stratification and nutrient availability can impact NPP, which in turn affects marine biodiversity. This research underscores the importance of understanding NPP-biodiversity dynamics for developing effective conservation strategies. While the prevailing trend in marine ecosystems is a reduction in NPP in response to ongoing climate change, local trends may vary due to the influence of other environmental variables, resulting in a higher level of uncertainty. Using easily accessible satellite data, such as NPP, to inform biodiversity expectations could be a valuable tool for planning and managing conservation policies. Our study contributes to this understanding by integrating comprehensive data and emphasizing the need for adaptive approaches in marine conservation amidst changing global conditions.

Biological invasions are one of the major drivers of biodiversity loss. Efficient conservation efforts require knowing where negative impacts on biodiversity are likely to occur in the future, taking climate change into account.

The environmental impact classification for alien taxa (EICAT) is a well-known standardized system adopted by IUCN to score and compare impacts of alien species to native biodiversity and can be potentially used to predict invasion threats to biodiversity in Europe. We selected 100 terrestrial alien plant species known for their high potential for impacts. For each of them, we (i) assessed the EICAT impact score, (ii) fitted ensemble species distribution models and (iii) matched impact scores and geographical distributions across alien plant species to map the risk of biodiversity loss due to plant invasion in Europe, in the present and in 2050 under different climate change scenarios.

Preliminary results showed that several species with major impacts, inducing local extinctions of native species, have the potential to spread widely throughout Europe. Coastal, mountain and northern regions showed higher potential increase in the intensity of impacts in future climatic scenarios. Competition with native species in invaded communities, chemical and structural impacts on ecosystems were the most common mechanisms though which these alien plants are likely to affect biodiversity in Europe.

This study employs a modelling approach to assess the impact of climate change on four key species—Quercus cerris, Fraxinus angustifolia subsp. oxycarpa, Phillyrea latifolia, and Pistacia lentiscus—within a Mediterranean forest ecosystem. Field measurements, obtained using an infrared gas exchange analyser, inform the calibration and validation of a modified Farquhar and Caemmerer biochemical model of photosynthesis. This species-specific model simulates instantaneous net assimilation (μmolCO₂/m²s), stomatal conductance (mmolH₂O/m²s), and transpiration rates (mmolH₂O/m²s). To account for each species’ unique water-use efficiency, we incorporate marginal carbon cost theory in transpiration estimation.

By integrating model results over time, we obtain gross and net primary productivity, and transpiration values for each species under current climate conditions (2022) and future climate change scenarios (Shared Socioeconomic Pathways (SSP) 2.6 and 8.5). Key findings include:

1. P. latifolia and F. oxycarpa exhibit reduced annual net primary productivity under the SSP 8.5 scenario (179 and 624 gC/m²y) compared to 2022 levels (227 and 674 gC/m²y).
2. Conversely, P. lentiscus and Q. cerris demonstrate increased annual primary productivity in the SSP 8.5 scenario (872 and 425 gC/m²y vs. 828 and 392 gC/m²y of 2022).
3. Annual transpiration values are expected to rise for Q. cerris and P. lentiscus (from 392 and 484 gH₂O/m²y in 2022 to 444 and 532 gH₂O/m²y in SSP-8.5), while decreasing significantly for F. oxycarpa (from 674 gH₂O/m²y in 2022 to 227 gH₂O/m²y in SSP-8.5) and marginally for P. latifolia (from 227 gH₂O/m²y in 2022 to 206 gH₂O/m²y in SSP-8.5).

The model provides insights into how different species respond to climate change, which can be useful in guiding conservation and management strategies in ecological restoration projects.

Freshwater ecosystems play a crucial role in providing globally relevant ecosystem services. Yet, freshwater communities worldwide have experienced substantial declines due to human-driven changes, with non-native fishes and global warming identified as major threats. Although it is known that most fish are ectotherms, thus metabolically influenced by temperature, the effect of warming on fish impact has often been overlooked.

Among freshwater fishes, the eurythermal Micropterus salmoides is one of the most widely introduced and invasive species. Its predatory pressure has altered species composition and size structure of invaded communities, with M. salmoides often becoming the dominant predator. Although the species has been increasingly studied over the last few decades, the role of temperature in its predatory impact has only been marginally considered.

In this manipulative laboratory study, Functional Responses (FRs), describing the feeding rate as a function of prey density for M. salmoides and trophically analogous fish species (Esox cisalpinus and Perca fluviatilis), provided valuable insights into the effect of temperature (+3-6 °C increases) on predatory response and outcomes of competition between these predators. An increase in functional response (+418%) on prey populations with rising temperatures was recorded for the invasive species. Conversely, decreases in functional response and increases in mortality were recorded for the native ones. The differences in FRs were related to changing prey handling (which includes capture, consumption, and digestion of prey and defines the magnitude of the FR curve) with temperature.

The study highlights that the impact of M. salmoides on prey populations is expected to increase with warming, while native predators may experience a reduction in their competitive capacity, with implications for species coexistence and food web dynamics. Investigating the effects of biological invasions and climate change separately is therefore not sufficient for accurately measuring ongoing changes and appropriately managing ecosystems.