Modelling climate change induced phenological trends and frost risks in
Belgian fruit orchards
Abstract
Apples and pears represent an important share of Belgium’s horticultural
production but the sector has been subjected to a range of challenging
meteorological conditions over the past decade. The most disastrous
event was the extraordinarily severe frost night happening during peak
flowering of commercially grown apple cultivars, in April 2017. This
research aims at investigating how meteorological hazards in Belgium
will evolve in space and time with changing climate and at challenging
the claim of the insurance sector that the hazards are spatially
invariant. It features the assessment of the probability and severity of
frosts during the flowering period throughout the 21st century, using a
set of regional climate model realizations from the CORDEX ensemble. To
this end, the apple and pear tree phenology is modelled using the strong
relation between air temperature during winter/early spring and dormancy
break and consequently flowering. Local observations since 1950 of the
phenology of major cultivars indeed confirm a shift in phenological
stages in relation to warmer winters as an effect of climate change.
Preliminary results from sequential phenological models, running on
future daily mean temperatures, suggest that both the onset of flowering
and the last frost event in spring are likely to occur earlier in the
year, so that the challenge is to determine which trend is dominant and
how the return periods of severe frost nights (< -2◦C) during
sensitive stages evolve. Thereby, differences between cultivars and
between orchard locations within Belgium are taken into consideration.
Furthermore, the potential impact of shifting temperature regimes on the
pollinator activity during the blossom period is taken into account,
knowing that the most commonly commercially employed bee species are
sensitive to colder and more variable temperatures. The distinct
resulting hazard maps can be used to support decision making regarding
adaptation and prevention measures at the field, farm and regional
scales. Further downscaling will be possible by considering local
pedologic and topographic conditions, while for validation, data about
damage compensation claims will be used.