Nature’s Calendar is our phenology initiative, which, thanks to the efforts of an army of volunteers, observes and records the timings of natural events throughout the year.
These observations combine to produce the longest written biological record of its kind and tell us for certain that spring is arriving earlier.
Of course, no two years are ever the same and some are warmer than those that follow. But the weather is simply the noise within which there is an observable trend in the underlying climate.
Meteorological data are confirming and often exceeding predictions. According to NASA, the global mean surface temperature is almost one degree Celsius warmer now than in 1880. The minimum extent of sea ice is falling by over 13% each decade, resulting in sea levels rising at a rate of 3.4mm every year.
Weather vs climate
This global warming, the result of atmospheric greenhouse gas emissions, is driving climate change. The two terms are often used interchangeably but this causes confusion, especially where it’s not easy to relate the idea of higher temperatures with the observed weather, as is so often the case in the UK!
The Met Office’s UK climate projections suggest that all areas will be warmer by the 2080s, with summers warming more than winters. Rainfall patterns will change, with more winter precipitation (less likely to fall as snow) in the west and less summer rain generally.
In addition to these long-term changes, the UK could also experience greater numbers of more immediate weather events, such as drought or severe storms. If wildlife is already stressed by the underlying climate the impact of these events could be amplified. Major storms, such as the infamous Great Storm of 1987 in which 15 million trees were blown down, transform landscapes and do not necessarily result in complete recovery.
The winter roulette
Extended cold periods present a life-or-death challenge to many species and help keep nature in balance. Overwintering insect populations are winnowed out, limiting their numbers in the following spring. This process reduces the impact of pest species on their hosts, creating time for co-adaptation.
Milder winters will reduce the extent of the selective sweep acting on new arrivals into the country, allowing them a better chance to take hold. This is especially worrying because newly arrived species often lack natural predators so have the potential to become invasive.
Recent examples of invasiveness include;
- Himalayan balsam,
- Harlequin ladybird,
- Ring-necked parakeet.
Many pests and diseases of our native trees will be more likely to successfully overwinter and become established.
Seeds of doubt
Many plants, including trees, use dormancy to delay the germination of seeds until the conditions are right. Dormancy comes in many forms: an example of physical dormancy is where a seed has an impermeable coating that protects it as it travels through the digestive tract of an animal, only germinating when it is finally deposited in its own dollop of "manure".
Occurs where a seed has an impermeable coating that protects it as it travels through the digestive tract of an animal, only germinating when it is finally deposited in its own dollop of "manure".
Is broken only after growth regulators or inhibitors have been leached from a seed after a period of time in water, which could be from meltwater heralding the end of winter.
Occurs in response to changes in the seed’s internal status or external conditions, such as light period or temperature.
A changing climate will inevitably impact on the factors that control germination. This could lead to changes in the composition of our woodland species and alter their distributions across the landscape. A general rule of thumb is that many species will head north and/or uphill, but there are many variables in play: temperature, carbon dioxide concentration, rainfall patterns and wind speed to name a few.
What can we do?
1. Join up habitats
For wildlife to move, the landscape needs to be ecologically connected. Many woodland species are notoriously slow or unwilling to move across non-woodland habitats. Connectivity can be improved through non-woodland trees in the landscape, such as in fields and hedgerows. Unfortunately, these are precisely the trees that have been lost more than any others over the last couple of centuries, with millions more now threatened by diseases such as ash dieback and acute oak decline.
2. Reduce carbon in the atmosphere
Trees absorb carbon dioxide from the atmosphere, mix it with sunlight and turn it into wood. Planting new trees and woodland is the best way of reducing atmospheric carbon and helps reverse global warming. Trees will also help us adapt to climate change, by providing shade in the summer, shelter from wind in the winter, and mitigating flooding risks.
3. Protect the landscape from extreme weather
Trees will also help us adapt to climate change, by providing shade in the summer, shelter from wind in the winter, and mitigating flooding risks.
4. Become resilient
Above all, climate change heightens the need for resilient landscapes. We need more woodland in bigger patches, to buffer and extend our remaining ancient woodland, and to connect woodland and other semi-natural habitats better.
Trees have a vital role in helping to limit the worst impacts of climate change and providing the means to adapt.
Discover what we’re doing about global warming
Find out more about the phenology initiative Nature’s Calendar
Find ancient and veteran trees near you by visiting the Ancient Tree Inventory