Thousands of people are taking part in national scheme called Nature's Calendar, aimed at gauging the effect of climate change.

Experts say many plants and animals are already behaving differently in response to global warming.

They believe it's being played out in a race between the oak and the ash tree.

click here to watch Kim Barnes' report in full

As global temperatures rise, it looks as though the Oak may win.

It tends to come into leaf first in early spring, because it responds more quickly to warm temperatures.

The Ash responds to light - meaning that it could find itself crowded out by the oaks.

Keeping a check on the numbers of Oak and Ash trees is part of a huge national project undertaken by the Woodland Trust.

Seventeen thousand volunteers are monitoring when natural events happen, from the first cuckoo in Spring to the exact dates when plants flower.

The hope is that this information will enable scientist to protect some of the species which will find it more difficult to adapt to Britain's changing climate.