Tag Archives: ecology

Sahara Dust and Irish Rain

Now that it’s Autumn Ireland is suffering some very damp weather, and Wicklow is experiencing a ‘classic’ Autumn, cold wet and muddy, but quite beautiful too. This is largely the result of two very warm and balmy summers in a row –  not in Ireland but in Africa, in the Sahara Desert. After hot summers in North Africa huge amounts of dust are blown westwards out into the Atlantic Ocean.

The direction of Saharan dust and how it travels around the Atlantic and brings heavy rain to Ireland and the rest of Europe.
The direction of Saharan dust and how it travels around the Atlantic and brings heavy rain to Ireland and the rest of Europe. Ireland is marked in red.

Some of the dust is carried northwards directly into the Bay of Biscay to the south of Ireland, but most goes to Brazil in South America and the Caribbean. Some of the dust lands on the Brazilian coast where it has been directly identified as damaging the rare coastal cloud forests. Much of it lands in the Caribbean where it sinks to the sea floor and smothers coral reefs, in some cases directly killing them.

The lighter dust that doesn’t land on the sea begins to do something quite different. At the heart of every single drop of rain lies a tiny particle of dust. Water molecules evaporating from the ocean are attracted to this dust and slowly begin to collect around it. The dust is carried from the Caribbean on the air currents that flow above the Gulf Stream, the same current that keeps our temperatures mild despite the fact that the island of Ireland lies very far north. When they arrive over Ireland’s southern coast the combination of cold land air and the fact the droplets are too heavy to stay airborne causes them to fall in torrents, sometimes causing terrible flood damage to coastal communities in the south west.

The rains of autumn are going to get worse over the years, for the simple reason that the Sahara is expanding at ‘an alarming rate’. How and why this desert originally began to form throusands of years ago is still something of a mystery, but the cause of its rapid expansion in the 20th and 21st centuries is not a mystery – UN studies have found that it is largely due to cattle-farming in sub-Saharan Africa.

Areas around water sources begin to suffer extreme climate change and erosion because grazing animals congregate within only a few hours walking-distance of them. These 10-12 km desertification circles around drinking wells were identified and termed “Piospheres” by an Australian ecologist, Dr. Robert Lange, as early as 1969. The width of these desertification circles exactly matches the distance that a bovine animal can travel in one night . The big problem now is that the population of sub-Saharan Africa has grown and led to a demand for more and more cattle, which has caused the Sahara to grow faster and faster.

So the secret to solving this problem can only be a change in farming practices, which will require a cultural change and the developments of new methods of irrigation to restore the damaged environments of sub-Saharan Africa.

Progenies of a Warm Summer

This year Wicklow was blessed by a very warm spring and summer. August has brought some heavy rain belts, most recently the remains of Hurricane Bertha, which passed across the island overnight, but all in all it has been a very good year. The most unusual thing I came across this year was a nest of Norwegian Wasps (Dolichovespula norvegica) which nested in a buddleia bush in my own garden. These wasps and the similar Tree Wasp look like the Common Wasp but make their nests only in trees and shrubs. It was my first time seeing them and they are considered a relatively new arrival in Ireland.  They can only be positively identified by the markings on their faces… and that isn’t easy to do but a camera makes it easier.

The nest of the Norwegian Wasps wound around the bracnhes of a butterfly bush, with some wasps perched on the outside.
The nest of the Norwegian Wasps wound around the bracnhes of a butterfly bush, with some wasps perched on the outside.

They soon got used to my approach, although were still in the habit of buzzing strangers who came near the gate. But in the last few weeks the wasp population has crashed across all species. Instead of wasps there are near identical hoverflies feeding on fallen fruit. But the butterflies are doing exceptionally well this year. Especially this beauty, the Small Tortoiseshell, which can be seen wherever there are butterfly bushes and warm walls and fences to bask on.

One of the most beautiful of our native butterflies, the Small Tortoiseshell is also long-lived and hibernates through the winter.This one pictured is feeding on mustard nectar.
One of the most beautiful of our native butterflies, the Small Tortoiseshell is also long-lived and hibernates through the winter.This one pictured is feeding on mustard nectar.

However, the damp conditions certainly suit some creatures, most especially frogs. We have only three species of amphibians on the entire island of Ireland, so far known – one species of frog, one toad and a newt. The European Common Frog (Rana temporaria) is thriving in Wicklow and with a little effort (and sometimes none at all) can be found in meadows, hedgerows, marshes and woods. It must be remembered that all amphibians in Ireland are protected species because their role in the ecosystem is so important. They are an essential pest-control.

A handsome specimen of Common Frog which was hunting for insects in a woodland.
A handsome specimen of Common Frog which was hunting for insects in a woodland.