On Friday 12^th August, the Environment Agency declared that due to this dry period, drought conditions have claimed eight out of fourteen areas throughout England. We have witnessed detrimental impacts throughout our ecosystems: including wildfires such as that seen across Pirbright Ranges, species loss due to lack of water sources (particularly seen in insect fauna), browning of horticultural crops and the noticeably premature shedding of trees dropping their leaves.

We are used to seeing the golden turning of colours as we welcome autumn during the latter end of the year, however this year we have experienced this much earlier than expected and for very different reasons. So, why are our trees dropping their leaves so early on in the year?

When plants uptake water from the earth through their roots, the water vapour is pulled against gravity up through the trunk and to the leaves where it will be evaporated along with other gases. Water vapor and these gases are able to escape into the atmosphere through small openings on a leaf’s surface known as stomata. Drought stress can cause the stomata to close to prevent water loss through evaporation. Once the stomata is closed, plants are unable to exchange gases and take in carbon dioxide that is required for producing carbohydrates needed for supporting growth. Unfortunately, extreme conditions are often too great of an impact and plants will drop their leaves and rely on reserved energy from spring and summer.

In addition, a term known as ‘summer or sudden branch drop’ is one used for trees dropping mature branches during the summer months, typically following heavy rainfall after prolonged drought. With this being said, although commonly suspected to be a result of weather conditions, the definitive cause for branch drops is yet to be determined. This condition is commonly seen in species such as Oak, Beech, Horse Chestnut and Ash. For tree species such as the Oak, premature dropping of unripe acorns will form the diet of many small mammals and deer species this summer. This high-energy food source will not contain the energy had it fallen once fully ripened later in the year. Sadly, this is likely to have a negative impact on wildlife that rely on such food sources to enact as a fat storage for winter.

As climate change continues to cause temperatures to climb, we are likely to experience further premature leaf drops earlier on in the year. An earlier leaf drop may result in trees drawing in less carbon dioxide over the year, therefore decreasing their potential as carbon sinks. The survival of drought-stressed trees will differ between flora species. As discussed above, the reduced capability to convert water into glucose needed for growing will mean a shorter growing season and may induce early winter dormancy. For many tree species, this will not be a problem as they can survive for prolonged periods without photosynthesizing. Nonetheless, increased frequency of droughts could lead to longer dormancy periods, resulting in decreased intervals to prepare for such conditions. Here we could see consequential changes in our landscapes.

Moreover, methods to conserve your garden flora during a dry spout include using a water butt to catch rain water to prevent the use of a hose, as well as laying mulch and bark in your garden to reduce up to 75% evaporation. Using link here, find out how the Surrey Wildlife Trust advises we conserve water to help the environment. Furthermore, here the Royal Horticulture Society advises on the best tree species to plant in preparation for foreseeable drought increase in the years to come.

In conclusion, the most efficient way to aid in conserving our flora here in the UK is through climate change action. Ways in which we can all fight climate change are highlighted by the Surrey Wildlife Trust here. Examples consist of dietary changes to lessen agricultural footprint, alternative travel options to reduce emissions, switching to a renewable energy supplier and increasing recycling/ upcycling. Through slight alterations to our day-to-day habits, we can live more sustainably and with combined efforts, assist in reducing the adverse effects of climate change.

Please find linked below some useful resources on topics discussed:

National drought group

Trees and drought

Global change biology

By Grace Brady