There is much talk about climate change these days (about
time!) and there is no better example of how this will impact on biodiversity
than the Zullich’s Blue, Agriades
zullichi.
This lovely little butterfly is endemic to the Sierra Nevada
mountains in southern Spain. It only occurs in 39 small colonies in a zone
between 2,500 and 3,000 metres in altitude.
The food plant of the caterpillars is Androsace vitaliana, a small clump-forming plant, only about 2cm
high, which grows on exposed slopes in the Alps, Pyrenees and the Sierra
Nevada. It grows in the same altitude range as the Zullich’s Blue.
It tends to grow in very fragile habitats of rocky scree
with very little vegetation cover. These areas are vulnerable to landslides,
trampling by cattle and most worryingly climate change.
When I first went in search of Zullich’s Blue in 2016, I was
amazed to see butterflies surviving in such windswept and exposed locations
The butterfly is only about 20 to 25 mm across its wings and
is well camouflaged. I love the subtle brown, grey and blue markings, but this
does make them very difficult to spot! They only fly in late June and July.
Average temperature in the Sierra Nevada has increased by 2° in the last 30 years and it
is projected to increase by a further 5 degrees in the next century. Snow is
now melting earlier in the season, leaving the sloped more exposed to wind and
resulting in the ground drying out.
This is a problem for the vegetation,
which really needs to move up the mountains to a cooler environment in order to
survive. Unfortunately, the dispersal of the seeds doesn't allow the plant to
spread far each season.
Similarly the timing of the emergence of the butterfly is
critical. If the temperature is warmer than normal, the butterflies may emerge
too early in the season to find flowers to feed on, or they could be laying
eggs on desiccated plants.
In order to adapt to the changing climate populations of
butterflies will be displaced upwards. Even if the food plant could spread
uphill in time to keep up, mountains get smaller the higher up you go.
Therefore there will be less suitable habitats available for this already rare butterfly.
Thankfully, there is
a lot of research going on in the Sierra Nevada about climate change and its impacts
on biodiversity. It is hoped that this will increase our understanding of how
climate change will effect species elsewhere and what can be done to help
species adapt.
I really hope that something can be done to help protect
this special little butterfly.
