Sunday 20 October 2019

Global warming a threat to nature's timing

Swallows usually lay 4-5 white eggs with variable reddish-brown markings
Swallows usually lay 4-5 white eggs with variable reddish-brown markings

Jim Hurley - Nature Trail

Climate change is an issue that is set to remain near the top of the scientific and political agenda for the foreseeable future. Mean global temperature is increasing rapidly, and that trend is anticipated to continue because of rising greenhouse gas concentrations.

One of the most widespread and well reported effects of climate change in recent years has been changes in the timing of events in nature. Plants are flowering earlier, frog spawn is appearing earlier in ponds, butterflies and moths are emerging earlier, migrants like the Swallow are arriving earlier and birds in general are nesting earlier.

The British Trust for Ornithology has collected data over a long number of years via its BirdTrack migration survey and its Nest Record Scheme. Analysis of the data confirms that bird laying dates are advancing by an average of almost nine days. Research has also confirmed that these changes can be directly related to spring warming.

Phenology is the study of the timing of biological events. Records of the date on which the first Swallow arrives show that these migrants from Africa are now arriving about 20 days earlier than they did in the 1970s. When they arrive, they need flies to eat so they obviously face a significant problem if the flies that they eat are not emerging 20 days earlier too.

All life is interrelated. The timing of trees budding, flowers blooming, insects emerging and migrants arriving all need to be synchronised to maintain the circle of life as we knew it in the past. Fine-tuning via evolution to correct any phenological mismatch happens very slowly. The present danger is that the accelerating rate of global warming is too rapid to allow for that fine-tuning leading to casualties along the way.

Findings from a 2015 EPA study indicate that by the middle of this century mean annual temperatures in Ireland will increase by 1-1.6°C, with the largest increases seen in the east of the country. Hot days will get warmer by 0.7-2.6°C and cold nights will get warmer by 1.1-3.1°C.

The number of frost days is projected to decrease by over 50%. The average length of the growing season will increase by over 35 days per year. Heavy rainfall events will increase in winter and autumn but decrease during the spring and summer months. Storms affecting Ireland will decrease in frequency, but increase in intensity, with increased risk of damage.

Wexford People

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