Plant phenology and climate change : possible effect on the onset of various wild plant species first flowering day in the UK

anglais. The IPCC states that the planet is significantly warming due to effects of climate change. This warming effect has consequences for phenological events. Many species cannot track rapid climate change, resulting in phenological mismatches. This study looks at an extreme weather event and the longer-term effects of climate change. According to the IPCC, extreme weather is linked to climate change. The study utilises geographical information science (GIS) tools to present the results of the possible relationship between climate change and the first flowering day (FFD) of the 5 species of wild plants. The results show that the UK has significantly warmed by up to 1°C during the period 1984 – 2017 compared to 1950 – 1983, confirming various IPCC reports in the literature that the GMST is warming. Various studies report that the winter of 2007 reflects an extreme weather event, where the winter was significantly warm. Regarding the short-term extreme weather events and their effects on FFD, the UK winter temperatures of 2006 were compared against the winter of 2007. The results showed that the winter mean daily temperatures in 2007 were significantly greater by about 2°C compared to 2006 (p<0.05), where the 2006 winter temperatures were similar to the 1961 – 1990 baseline average, confirming studies in the literature that 2007 experienced an extremely warm winter. The FFD of each species was compared between 2006 and 2007. The results showed that the mean FFD of all species significantly advanced between 13 and 18 days (p<0.05) during the extreme warmer winter of 2007 compared to the cooler (average) 2006 winter, confirming that FFD is affected by temperature. Regarding the longer-term climate change effects on FFD, this study looked at the spatial distribution of FFD based on simple linear regression using temporal data of time series with at least 15-years of FFD records at the same location. This provided a measure of the FFD response to temperature, with the notion that the strongest negative responses are linked to the warmest regions. The results from a total of 351 simple linear regressions showed that 74.6% were significant negative response rates (p<0.05) (FFD advancement - ranging from -3.5 to -6.7 days °C-1), 1.7% were non-significant positive response rates (p≥0.05), the rest were non-significant negative response rates (p≥0.05). Spearman rank correlations were conducted on the 74.6% of significant negative response rates in relation to latitude, longitude and elevation to determine if there was a spatial element that influenced the FFD temperature response rates. There was only one positive significant correlation and this was in respect of coltsfoot (p<0.05), where its response rate became increasingly more negative with decreasing latitudes, showing that this species’ FFD becomes more sensitive to temperature in the warmer regions of the UK, regarding a north to south distribution. Since no FFD temperature was recorded at the time of FFD data collection (this site-specific variable was required for the FFD/temperature response rates), temperatures were approximated from calculations using the Environmental Lapse Rate and 0.25° (WGS84) mean gridded temperature/elevation data supplied by European Climate Assessment & Dataset (ECA&D). Error induced, from using such coarse mean gridded data, may lead to less precision regarding temperatures at each FFD location. So, other methods may be required to reduce these possible errors by using finer resolutions, which provide more detailed information on localised terrain, such as those produced from LiDAR images, leading to greater accuracy in FFD location temperatures. Given that all species in the study significantly respond to increased ambient temperatures, where they advance their FFD, then, it is suggested, that they can act as climate change indicators, which can be included in earth system and ecosystem models as simple phenological variables. The use of GIS provides maps that are easy to interpret, providing relevant climatic information in relation to its impacts on the natural world (through phenology). Governments and non-experts can benefit from the visually appealing results, so that appropriate actions can be taken in possible mitigations to reduce the effects of climate change.

anglais. This report investigates the relationship between climate change and plant phenology. Phenology can be considered as the timing of biological events, such as the emergence of flowers in the spring in preparation for reproduction. Such events are influenced by factors like ambient temperature, which can instantly change based on weather patterns. Further, long-term changes to the climate can take place where, for example, temperature can gradually increase over a number of years, such that changes become significant compared to earlier time periods (usually measured in 30-year chunks). Global warming is considered a driver of climate change, which has largely resulted from human-induced greenhouse gas emissions over a long period of time. Such emissions include increased atmospheric carbon dioxide through fossil fuel burning, particularly coal, in the global generation of electricity for both industrial and domestic use. The aim of this study is to better inform scientific experts, governments and interested non-experts on the impacts of climate change, through the production of easily understood maps that show climate change is occurring, using a component of the natural world as an impact of that change. The first flowering day (FFD) is a phenological event, which can be thought of the first day in the annual calendar when flowers begin to emerge on a plant; this day can change from year-to-year depending on the ambient temperature. The FFD of 5 species of wild plants found in the UK was studied to determine if these plants could be used as indicators of climate change. The plant species studied were bluebell, coltsfoot, cuckooflower, garlic mustard and wood anemone, all of which are common wild plants found in many hedgerows, woodland areas and meadows throughout the UK. The FFD and location of the plants were recorded for each year between 1950 – 2017, such information was provided by the UK Woodland Trust. The ambient temperature for each FFD record in each year, of each of the plant species, was calculated to see if there was a relationship linking climate change to the timing of the flowering events. Temperature, a component of climate, is considered a prominent variable that drives changes to plant FFD in temperate regions such as the UK; many scientific studies have concluded that ambient temperature has a significant effect on plant FFD. The results from this study found that the UK average ambient temperature had significantly increased by up to 1°C during the period of 1984 – 2017, compared to 1950 – 1983. This study also found that the FFD of all the wild plants species investigated is affected by changes in ambient temperature, where increases in early springtime temperatures show a related advancement in FFD. The results from this study were produced as maps, through a software program known as ArcGis, that present the effect of climate change on the first flowering day of the species studied. Many species, both animals and plants, rely on each other and interact based on phenology, such as flowers being pollinated by insects. Climate change may negatively impact these interactions because some species may react more quickly, than their interacting partners, to increases in ambient temperatures, for example, insects may not emerge to pollinate flowers should the flowering event occur earlier in the year due increased temperatures. This may lead to crop pollination problems and ultimately lead to human food shortages. This study found that each of the 5 species investigated could be used as indicators of climate change and, thus, could be included in climate change and ecosystem models as basic phenological components that could help predict future climate and ecosystem changes. Knowledge of the changes to phenology brought on by climate change can be extremely useful to governments, who have a responsibility to mitigate global warming through a reduction in greenhouse gas emissions. This would be achieved by national parliaments creating environmental protection laws that the public and industry must abide, a top-down approach. The general public may find the knowledge also interesting and important so that they can play their individual part in climate change mitigation. One individual’s part may only be small, but a huge collection of individuals taking part may produce great mitigating change, a bottom-up approach. Thus, humans have a responsibility to look after the environment, not only to protect the many global ecosystems, but also to maintain food security for themselves. Well-presented results visualised in mediums such as maps, may enhance climate change knowledge and improve awareness on its impact on the natural world, thus, assist people in making good decisions on their environment.