Bio-indicators of Climate Change

Climate Change refers to long-term shifts in temperatures and weather patterns. Such shifts can be natural, due to changes in the sun’s activity or large volcanic eruptions. But since the 1800s, human activities have been the main driver of climate change, primarily due to the burning of fossil fuels like coal, oil and gas. Burning these fuels generates greenhouse gas emissions that act like a blanket wrapped around the Earth, trapping the sun’s heat and raising temperatures.

The main greenhouse gases that are causing climate change include carbon dioxide and methane. These come from burning fossil fuels but clearing land and cutting down forests can also release carbon dioxide. Agriculture and oil and gas operations are major sources of methane emissions. Energy, industry, transport, buildings, agriculture and land use are among the main sectors causing greenhouse gases (UN.org).

Ireland’s annual average temperature has increased by approximately 1°C over the last 100 years, with 16 of the 20 warmest years occurring since 1990, and 2023 being the hottest year on record. Extremes of heat in Ireland (heatwaves) are becoming more frequent and more severe, while extremes of cold (cold waves) are becoming less frequent and less severe. Heavy rainfall events have been 7% more intense over the last 30 years. Satellite observations indicate that the sea level around Ireland has risen by approximately 2-3 mm a year since the early 1990s (EPA Ireland’s State of the Environment Report 2024).

Overall Ireland’s climate is predicted to become more changeable and wetter, with more stormy weather, but with higher average annual temperatures. Projected Climate Change impacts for Ireland include impacts on biodiversity, with an increase in invasive species, competitive pressures on native species, and changes in species ranges and phenology.

When we look at species distributions, those with restricted distributions around the Irish Coastline are good candidates for climate change bio-indicators. These could be warm-water species with distributions restricted to the south coasts, or cold-water species with distributions restricted to the north coasts. We also look for newly arriving species, usually warm-water species not previously recorded in Irish waters and species which show an unusual change in abundance – becoming much more common or more rare than they were previously.

Another good group for potential bio-indicators are those with distinct peaks in their occurrence, such as jellyfish. We can monitor these ‘peaks’ over time to see if they are changing with changes in average annual sea temperatures.