The public may need to accept that lawns will be yellow during dry summers
Fields, parks and lawns across Europe have turned to straw this summer. Landscapes thousands of years old have been revealed as green outlines against yellow backgrounds, where ancient underground walls and ditches retain enough water to sustain pockets of grass above them. Lawns and parklands have been especially affected because what water is available is being directed to homes and farms.
July was the driest month ever recorded in England and Wales, and droughts have affected parts of Britain in four of the last five years. As heatwaves become more frequent with global warming, this raises an uncomfortable question for a country that takes particular pride in its greenery: what happens to “England’s green and pleasant land” if summers like this become the norm?
The news isn’t all bad. As a group, grasses are good at surviving dry conditions, and their resilience has helped make them one of the most successful groups of plants on Earth. They now include more than 11,000 species and cover more than 40% of the Earth’s land area, from tropical savannas to Arctic steppe.
They are also much older than scientists once thought. The earliest fossil grasses date to around 55 million years ago, but distinctive mineral deposits in their leaves have since been found in fossilised dinosaur faeces from the late Cretaceous period so we now know that grasses were around tens of millions of years earlier.
Grasslands only spread across the world later, about 20 to 30 million years ago, when they took advantage of a climate that was becoming cooler and more arid. In those conditions, grasses could survive better than many other types of vegetation.
The main grasses used in British lawns, however, are not necessarily as well adapted to dry conditions as some of their relatives elsewhere. But even species already native to northern Europe and well adapted to cool, damp conditions have ways of surviving drought. They can slow water loss from their leaves and, where possible, send roots deeper into the soil in search of moisture.
But under really dry conditions, such as those we are seeing at the moment, they have no choice but to shut down and wait for better conditions. They move what water remains to the parts of the plant that will produce new leaves, which are protected deep inside the outer leaves. These outer leaves dry out and die, giving some of their water to the critical growing parts, which survive and are ready to produce new leaves when it rains again. The growing centres also accumulate sugars that help draw in water and protect their cells from drying out.
Stuart Thompson is an Emeritus Fellow in Plant Biochemistry at the University of Westminster.
This article is republished from The Conversation under a Creative Commons licence. Read the original article.