I remember when we'd found out
that Wytham had ash dieback,
and my first reaction was,
my goodness that's really bad,
about 90% of all the ash trees will die.
This has been a silent pandemic
that is fundamentally shaping
the nature in Western Europe.
The thing I really like about ash is
how beautiful the tree is
and it's really sad to think
that those trees will go.
It's a beautiful tree, the ash tree.
It has a lovely bark, lovely leaves.
Because it has a semi open canopy,
it lets light through to the forest floor.
Just walking around
a high abundance ash area is a joy.
The simple loss of such a beautiful
and iconic tree will be a psychological loss.
Ash dieback is a fungal disease called
hymenoscyphus fraxineus.
It's an alien species that came over from Asia,
probably on the timber trade,
first being detected in Poland in the early 1990s,
and then it came to the UK in around 2012.
But we didn't detect it in Wytham until about 2017.
Wytham is a terrific place to study ash dieback,
both in how it's affecting the ash trees,
and also how it's affecting the wider ecosystem.
And that's because it has such a long history
of studies of the mammals, the birds,
the other trees, the soil.
What we're doing over the next few years in Wytham
is trying to bring together all those range of studies
to understand that when you take out the ash trees,
how does that cascade through an entire ecosystem?
The ash dieback project is a four year project,
which means that we have to do something
to project into the future.
For that we have three different types of plots.
So we have a control plot without any ash at all,
projecting really far into the future,
when all the ash trees have died,
and other tree species have recolonised that plot.
We then have a plot with a lot of ash.
And then a third plot,
which is also very high in ash abundance,
but we're going to kill all the ash trees,
and that's projecting into the future,
maybe 10 to 15 years.
When you start opening up that canopy with lots
of tree death, you're going to have
areas of more light coming through.
Then we might expect for example
the bramble and the understory
to get more dense because of that extra light.
Ash is really important because it's got
these very palatable leaves,
really soft, incredibly yummy.
And these leaves break down
incredibly quickly, in four to six months,
which means that there's more nutrients
in the soil for the trees to take up and grow.
So if you remove the ash tree,
you're basically slowing that system down.
One of the fascinating things about
a change in an ecosystem is that
there are winners and losers,
and there are also different processes
determining what you win and lose.
So if you take the mindset of a small mouse,
what determines how successful that mouse is?
On one level it's determined by how much food there is.
If ash disappears,
the food supply might diminish over time.
The other thing that threatens
that little mouse is being eaten.
So as the forest becomes more shrubby,
and more light comes through,
that mouse may also be under less pressure
from being eaten from above.
Plant diseases, in some ways are natural,
but the increasing frequency of diseases
is one of the features of global change.
And this is because increasing travel
and trade and movement means that
diseases spread more quickly.
Trade has certainly played a role in moving
ash dieback across Europe and into the UK.
This is not the first time and it's not the last time
a mass mortality event like this will happen.
With climate change, these things will probably
become a little bit more frequent.
So just working on a project where we can
actually figure out what will happen
so that in the future this can be of some use,
I think it's a nice feeling,
even though there is a lot of death.
I love ash trees, so I do feel wistful
to know how much that this woodland
is going to change.
I won't be able to walk through groves
of ash tree with the light dappling through
probably in five or ten years time.
However, I think my ecological hat tells me
that change is always occurring in ecosystems
in one way or another.
The ecosystem of Wytham Woods
and the richness of the ecology and the
interactions will be here for decades to come.