Portents and Pollutants

Originally published May 2015

Hello everyone! As we say farewell to the first third of the year I am left wondering why everything seems to have been so reluctant to go forth and multiply. Given that we had an extremely mild winter and a goodly amount of rainfall early in the year you would think Ma Nature would have taken advantage and set everything in motion long before now. It could be that the chilly easterly that insists on sweeping across every now and then is keeping our fauna and flora in check, and perhaps the old girl knows something we don’t!

Despite the delays, we have Wood Anemones, Lesser Celandine, Spotted Orchids, Wild Garlic and Bluebells lighting up the woodland floors whilst the creamy flowers of the Blackthorn seem to flow out of the hedgerows. Tadpoles are wriggling in the pond and bees, wasps, hoverflies and the odd butterfly are busy in garden and woodland alike. The Feathered Folk are occupied with nest building and the air is full of their song. Unfortunately the spectacular Avian Proms did not really feature this year, unless, of course, I slept right through it!

So much for what is out and about at present, but what can we infer from all of this timely activity? Since time immemorial we have used natural occurrences in an attempt to predict the seasons, harvests or, more commonly in this country, the weather, and we have numerous words of wisdom to cover every eventuality. Meteorologists can provide the science behind the familiar old maritime adage, red sky at night, sailor’s delight, red sky in the morning, sailor’s warning, or as the Bard put it so eloquently in his poem Venus and Adonis (1592-93):-

Like a red morn that ever yet betokened,
Wreck to the seaman, tempest to the field,
Sorrow to the shepherds, woe unto the birds,
Gusts and foul flaws to herdmen and to herds.

Other anecdotes have their origins in the mists of time after generations of nature watchers have interpreted their observations. High-flying Swallows, cackling geese, jumping trout, web-spinning spiders, acorn crops, morning toadstools, the list of signs and portents is endless; many with some credence to them and just as many confined to the pages of mythology. For example, When the Dogwood flowers, there will be no more frosts refers to the plant’s sensitivity to temperature, whereas Oak before Ash; in for a splash has a less than scientific explanation and has no real foundation in truth.

These days we have an extra consideration when interpreting what we see around us, the anthropogenic factor, how human activity has affected the biosphere and the fauna and flora within. The sensitivity of various organisms to fluctuations in their surroundings is the basis of environmental science and we now study communities of organisms in order to monitor the health of the environment or that of a particular ecosystem. Thus was I found, twenty or so years ago, waist deep in freezing mountain streams on the outskirts of Edinburgh looking for samples of filamentous algae to take back to the science lab. Apart from eliciting such comments as ‘that’ll be a bit nippy up your Trossachs!’ from my pals, I managed to complete my thesis on the correlation between algal species and the acidification of fresh water. A year later I completed another thesis on marine phytoplankton blooms and the eutrophication (nutrient loading) of the chilly waters of the Firth of Forth.

PJ scotland 1

All this gratuitous reminiscing is not just a blatant bit of self-indulgence, but hopefully offers a small insight into the amount of research involved when dealing with biological indicators. Some may question their use when we can just carry out chemical tests on samples of water, soil and even air. These give an accurate picture of the condition of the environment or habitat, but only at the time that the sample was taken. These ‘snapshots’ can be very useful in situations that change rapidly such as a chemical spill into a water course or a sudden release of toxic fumes into the air. However the health or longer term condition of an ecosystem can be judged only by studying those organisms that inhabit it. Certain species, such as lichens, are biomonitors. Their presence on rocks and trees is a general indication of good air quality as they are sensitive to sulphur-based pollutants and nitrogen oxides.

Biotic indices are used to grade the quality of water. The Biological Monitoring Working Party (BMWP) is a biotic index designed to ascertain the biological condition of rivers in Britain. Samples are taken using a three minute sweep or substrate-kick into a net. The taxa are identified to Family (see What’s in a Name? Dec. 2009) only and each one given a score between 1 and 10. Those Families that are least tolerant to pollution such as Mayflies and Stoneflies are given the highest score whereas Worms and Midges, being the most tolerant are at the other end of the scale. A higher BMWP score, the sum of the tolerance scores of the invertebrate Families in a sample, is deemed to reflect a higher water quality. Of course, as in the case of chemical testing, we need to know what we are looking for and be aware of the limitations of the system. The BMWP was developed to measure responses to organic loading and oxygen depletion and is unsuitable for detecting other forms of pollution. For instance the presence of Stoneflies indicating good oxygenated water does not preclude the presence of heavy metal pollution from mining activity which they are markedly more tolerant to.

Some creatures reflect changes in their environment by literally evolving to cope with the new conditions. The Peppered Moth (Biston betularia) is used as a model species to demonstrate Darwin’s natural selection in action. During the nineteenth century the moth was observed by naturalists to prefer lichen-covered trees and rocks where its light colouring enabled it to be practically invisible to predators. In 1845 a dark coloured specimen was recorded in the industrial area of Manchester. Increased industrialisation in Britain killed off the Lichens as smoke particles polluted the foliage turning both trees and rocks black, making light-coloured moths easy targets for birds. More and more dark moths were recorded and by the 1950s very few light-coloured specimens were found. Who knows how many other cases of microevolution we are causing through our activity?

We will have the opportunity of studying the moths on our own little reserve in July when Ralph Hobbs from the Powdermill Trust will be setting up a moth trap for one night only. Details to come! Ultimately we just have to enjoy each season and the wonderful plants and animals that come with them. Treasure our environment, enjoy the wild flowers, insects and birdsong and hope they return for many years to come.

Gone were but the Winter
Come were but the Spring,
I would go to a covert
Where the birds sing.
Spring Quiet – Christina Rossetti (1847)

Paul Johnson

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Still splashing about in the water!

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