Changes in temperature, rainfall and extreme weather events affect animals, plants and natural resources in a profound way, including timing of plant germination and flowering, the migration and breeding patterns of wildlife, and soil stability – to name just a few.
Extreme rainfall can damage habitats
Heavy rainfall can cause ditches, rivers and streams in the parks to swell, and the ground to become waterlogged, resulting in localised flooding. When combined with areas of heavy footfall saturated areas of ground can be transformed into mud baths – not just an inconvenience for visitors' shoes, but can cause significant damage to habitats alongside footpaths as people seek drier ground. In Sites of Special Scientific Interest (SSSIs) such as Richmond Park and Bushy Park this can have a huge detrimental effect on rare and important plants and animals, including their important acid grasslands and veteran trees.
With support from players of People’s Postcode Lottery we are undertaking a large-scale project in Richmond Park and Bushy Park to reinstate damaged footpaths and protect and restore vulnerable habitats, such as acid grasslands and the ant hills found there.
Dry periods can harm freshwater species, such as great crested newts
Periods of drought can result in water levels in ponds and lakes falling rapidly, and wetland areas drying up. This can be of particular concern for amphibians, such as the protected great crested newt, with a recent pattern of very low rainfall early in the year of particular concern as the early drying of ponds prevents the completion of amphibians' life cycles (as well as other aquatic wildlife). In spring of 2021 some ponds where the newts live dried up before eggs had time to hatch, or juveniles to mature and leave the pond.
In the long term this will impact amphibian populations by reducing breeding success, potentially even causing localised extinctions.
Recent research led by ZSL, University College London and Queen Mary University of London found that global warming has also increased the spread and severity of a fatal amphibian disease caused by Ranavirus, which has impacted common frog populations in the parks and throughout the UK.
On land, prolonged dry periods in the summer can impact important food sources for species feeding on soil invertebrates. Hard and sometimes compacted ground can be impenetrable for species such as hedgehogs, blackbirds and thrushes trying to access those vital sources of food.
Invertebrates are emerging earlier
We know climate change is causing many invertebrates to emerge earlier or to alter their distribution (typically expanding northwards or to a higher altitude).
It’s a delight to see some new species colonising the parks, such as willow emerald damselflies in Richmond Park and Bushy Park, and interesting to observe buff-tailed bumble bees surviving the winter in Kensington Gardens – certainly a result of warmer temperatures in the city and the availability of winter flowering plants in the park.
However, other species adapted to cooler conditions are undergoing contraction in their ranges. And as species respond to environmental change, the interaction between them may also alter including those important predator-prey relationships. For example, the egg hatching time in some birds is falling out of sync with peak caterpillar abundance – meaning a reduction in the availability of a critical food source.
Birds are breeding earlier
Conservation Officer, Tony Duckett, has been observing wildlife for decades and has noticed significant changes in the parks’ bird populations.
The willow warbler, a migratory bird arriving in the UK in spring, was once commonly found in the south of England. Climate change has shifted the life cycle of the invertebrates that they feed on, meaning that the birds have shifted their range north where spring arrives a couple of weeks later. For a bird that only has one brood per year, the timing of the food supply is critical so a few weeks’ difference in the arrival of spring can make a huge difference to survival.
As winters have become milder with fewer cold spells many birds are breeding earlier, including the grey herons in The Regent’s Park. The majority of nests now become occupied by mid-February, but in winter 2021/22, one pair was spotted incubating eggs as early as December! Early nesting can be risky as food resources may not be sufficient for the survival of offspring, and a sudden cold spell with frozen, inaccessible water would prevent the adults sourcing food for them and their young.
Cetti’s warbler, an insect eating bird, has been spreading northwards through Europe since the 1970s. Finding insects during the winter can be hard and a sudden cold snap can kill a large percentage of the birds in the UK. Three of the Royal Parks have had pairs of Cetti’s warbler breed and overwinter, with Regent’s Park being the most recent site to host this bird.
The effects of climate change on trees
Trees are also impacted significantly by climate change. There are over 170,000 trees across the parks, and the effects of global warming on them are becoming increasingly more obvious and concerning. Heavy rainfall can lead to waterlogging of sites, which can damage or even kill trees. Warmer conditions can lead to an increase in pests and diseases such as oak processionary moth, and drought stress in periods of prolonged low rainfall weakens trees, making them more susceptible to attack and damage from pests and diseases.
Changing weather patterns also disrupt the established development of tree species. For example, late frosts may disrupt flowering and leaf bud burst, whilst trees in full leaf are at greater risk from an increase in unseasonal storms.
