Radiant energy from the sun falls on the Earth; some of this energy is absorbed by the planet and its atmosphere. Some of the energy is radiated back into space. The balance between the absorbed and radiated energy determines global temperature. This balance is changed by a number of factors - the intensity of the solar energy, cloud reflectivity, the absorption of energy by various gases or surfaces.
The reflectivity of the Earth’s surface (the albedo) influences the amount of light energy that is reflected back into space. Snow has a high albedo, that is, it reflects much of the light back out into space. Dark objects (like conifer plantations) reflect less light / radiation and absorb more thereby trapping heat that would otherwise be reflected back into space. The amount of energy that is ‘retained’ is also influenced by the presence of particular gases in the atmosphere - the so-called 'greenhouse gases', notably carbon dioxide and methane. The amount of carbon dioxide in the atmosphere has increased dramatically from 280 ppm during the 10,000 years up to the mid-18th century to 415 ppm (as of 2019). This increase has certainly contributed to the changes in climate that we have witnessed in recent years - extreme weather events such as heat waves and flooding. Read more...
Dendrochronology seeks to gather information from the annual rings of trees, dated to their year of formation. As trees age, they form new distinctive rings, outward from the centre, and each year a circle of new, dead wood is formed (by the cambium) around the trunk of most trees. The annual rings form because the water conducting xylem vessels or early wood formed in late spring and early summer (when growth is rapid) are wider and lighter than those formed in late summer and early autumn, which are narrower and darker (sometimes called the late wood). A light and dark ring together constitute one year’s growth. In winter, there is no growth.
Trees and their annual rings are essentially long term recording devices that ‘house’ information about climatic variations, past climates and ecosystems; they can even offer insights into historical events. From an annual ring, it is possible to extract information about precipitation, temperature and other climate data about that year. Read more...
A number of initiatives both national and inter-national have focused on the possibility of large scale tree planting as a means of reducing the effects of climate change and keeping global warming below the critical 2oC threshold. Indeed, some researchers have estimated that restoring and creating forests could reduce atmospheric carbon dioxide levels by 25%, ‘sucking out’ some (extra) 200 gigatonnes of CO2 and locking it away in wood.
However, there are problems with this approach.
- Some estimates suggest that human activities have added a massive 600 gigatonnes of CO2 to the atmosphere over the millennia
- Restoring or establishing forests is not a ‘simple matter’ of planting some trees (albeit millions of them); there are technical and financial challenges (see * below, for exmple).
Declining bee populations in Europe have caused alarm in recent years and the decline has been attributed to a multitude of factors / causes, for example :-
- Climate change
- Pesticides - especially neonicotinoids
- Varroa mites
Phenology is about the observation of natural events, recording when things happen, for example, when horse chestnut and ash trees come into leaf, or when the first swifts or bumblebees are seen. These timings vary from year to year. Through the recording of natural events over many years, one can look for trends and see if they are correlated with changes in the weather or other phenomena.
Recent studies by researchers at Rothampstead, the Centre for Ecology and Hydrology, and the British Trust for Ornithology suggest that a number of different phenologies are changing. They looked at various insect and bird populations in a variety of different habitats (urban gardens, agricultural systems, sand dunes, grassland, woodlands etc). The broad conclusion was there was a “trend towards earlier phenologies for UK bird, moth and butterfly species across habitat types” . For example, aphids (which breed rapidly and can adapt to changing temperature quite quickly) now take flight some 30 days earlier in the year than fifty years ago. Such phenological changes have ‘knock on’ effects. For example, the earlier arrival of aphids can affect potato crops. Aphids spread plant viruses and young potato plants are more susceptible to viral disease than older, more mature plants. Read more...
The hedgehog was once a common visitor to urban gardens, but now its numbers are in steep decline. Our hedgehogs face a number of threats in the modern, urban environment. For example :
- Being hurt by a pet dog
- Being hit by a car
- Ingesting slug pellets (metaldehyde - a poison)
- Becoming entangled in netting for growing peas / beans
- Getting stuck in a discarded tin can
- Entanglement in discarded rubber bands
- Being burnt in a bonfire whilst hibernating / sheltering
- Being wounded by garden implements eg. strimmers
Following the First World War, the UK’s woodland coverage was at an all time low – just 5 per cent of total land area. The Acland Committee reported to then Prime Minister, David Lloyd George, that state organisation would be the most effective way to bring about re-afforestation of the UK and plan for the future of British woodland.
As a result, the Forestry Commission was set up and, throughout the early decades of the twentieth century, it voraciously bought up land. The aim of the Forestry Commission was to ensure that there would be a strategic reserve of timber, so, as it acquired land, it began to plant - mainly with conifers .
‘Low grade’ lands (those that were less in demand for agriculture) were pressed into service such as areas around Thetford Chase and Kielder, as were some sandy coastal sites (e.g. Holkham in Norfolk Read more...
The science journal Nature has published the results of another insect survey, specifically of pollinating insects. The UK pollinator monitoring scheme looked at some 353 species of bees, bumblebees and hoverflies. The survey analysed 700,000+ sightings of pollinating insects over thirty years or more (1980 to 2013). The survey yielded information about the changes in the range of these different pollinators - that is the different parts of the countryside that these insects were found in. The survey did not attempt to determine actual numbers of bees etc in an area. There were “winners and losers’ in the survey but the overall picture was somewhat depressing. Read more...