Assessment of Climate Change Impacts on Chilling and Forcing for the Main Fresh Fruit Regions in Portugal

Abstract

Air temperature plays a major role in the growth cycle of fruit trees. Chilling and forcing are two of the main mechanisms that drive temperate fruit development, namely dormancy and active plant development. Given the strong sensitivity of these crops to air temperature and the foreseeable warming under future climates, it becomes imperative to analyze climate change impacts for fruit trees. The fruit sector in Portugal has risen significantly over the last decades, gaining increasing importance both internally and through exports. The present research assesses the impacts of climate change on the chilling and forcing for economically relevant fruit trees in Portugal, namely apples, oranges, pears, and plums. To assess temperate fruit chilling and forcing conditions, the chilling portions (CP) and growing degree-hours (GDH) were computed over Portugal, for the recent-past (1989–2005) and future (2021–2080) periods, following two anthropogenic radiative forcing scenarios (RCP4.5 and RCP8.5). Future climate data were obtained from four regional-global climate model pairs to account for model uncertainties. Bias-correction methodologies were also applied. A spatial analysis over the main regions with PDO “Protected Denomination of Origin” or PDI “Protected Geographical Indication” of origin of each fruit tree was performed. Future projections show a clear decrease in chilling for all regions and fruit types in Portugal. Nonetheless, given the current chilling values in Portugal and the relative importance of chilling accumulation for each fruit type, these changes are more significant for certain varieties of apples than for other types of fruit. Regarding forcing, the future projections highlight an increase in its values throughout the different fruit tree regions in Portugal, which should lead to earlier phenological timings. These changes may bring limitations to some of the most important Portuguese temperate fruit regions. The planning of suitable adaptation measures against these threats is critical to control the risk of exposure to climate change, thus warranting the future sustainability of the Portuguese fruit sector, which is currently of foremost relevance to the national food security and economy.

Agroclimatic Metrics for the Main Stone Fruit Producing Areas in Spain in Current and Future Climate Change Scenarios: Implications From an Adaptive Point of View

“…Important chill accumulation reductions are projected in all areas, which agrees with previous studies in Mediterranean areas ( Benmoussa et al, 2018 , 2020 ; Rodríguez et al, 2019 ; Delgado et al, 2021 ; Fraga and Santos, 2021 ). The chill accumulation decrease will be similar in absolute values in all the studied regions, but the warmest ones (i.e., Mediterranean area and Guadalquivir Valley) can be much more affected in terms of stone fruits cultivation suitability since their current situation is already a limitation for many cultivars.…”

“…Contrarily to chill accumulation, heat accumulation will rise in all the scenarios (especially in 2055_RCP8.5 as expected), and its evolution is inverse to this of chill accumulation. This was also observed by Fraga and Santos (2021) for Portugal.…”

“…Similar sudden drops in the near future were also observed by Rodríguez et al, who forecasted a decrease of up to 30 chilling portions for the period 2021–2050 in some locations in Spain ( Rodríguez et al, 2019 ), which agrees with our results. Benmoussa et al (2020) , Delgado et al (2021) , and Fraga and Santos (2021) also reported sudden drops between the historic and future scenarios in Tunisia, Portugal, and Asturias (North Spain), respectively. Like in our case, these studies also showed that no important differences for accumulated chill appear in the near future regardless of the RCP considered.…”

“…The authors also projected increases in heat accumulation, with a higher impact in the southern and coastal areas of the country. They highlighted that this fact may increase the risk of frost damage due to the advance of phenological stages ( Rodríguez et al, 2019 , 2021 ; Fraga and Santos, 2021 ) compared the current situation of the production areas of some temperate fruits in Spain with future climate change scenarios regarding chill accumulation. They forecasted important chill losses in some areas (e.g., South-East or Gualdalquivir area) even in the near future.…”

Variability of Phenological Behaviours of Wild Fruit Tree Species Based on Discriminant Analysis

“…Many phenological events, such as budding, flowering, and leaf occurrence; the timing of insect occurrence; or the arrival of migratory birds have advanced in response to recent climate change [ 6 ]. Numerous studies have documented the effects of recent climate change on plant phenology in a wide range of taxa [ 7 , 8 , 9 , 10 , 11 , 12 ]. Plant phenology affects the structure and function of terrestrial ecosystems and determines vegetation feedback to the climate system by altering carbon, water, and energy fluxes between the vegetation and near-surface atmosphere [ 13 ].…”