In recent times, new or different threats have emerged to upset the balance of woodland and forest ecosystems. In the 1960’s and early 70’s concern focussed on the effects of air pollution, particularly the effects of acid rain. This type of pollution was characterised by the deposition / assimilation of sulphur dioxide and its derivatives (sulphuric & sulphurous acid), plus various nitrogen oxides. This air pollution was largely due to industry and traffic.
Some of the most striking effects of ‘acid rain’ pollution were seen in the coniferous forests of Germany - where it was termed : Waldsterben [Wald=forest plus sterben=to die]. Read more...
Seeds are dispersed from a parent plant by a variety of means. Some plants use wind dispersal (sycamore, dandelion), some use animals (burdock, herb bennet), some even use water (willow, silver birch, coconut and the famous coco de mer). But in some parts of the world, such as South Africa and Australia, fire is a feature of certain ecosystems and the fire and/or smoke can be the stimulus for seed dispersal and germination. Read more...
The blog has reported on moorland fires and the importance of peat-based ecosystems on a number of occasions. However, a new report has raised serious concerns about the state of peatlands, not just in the U.K but across Europe and Scandinavia. Many ‘peatlands are in a dry and fragile state’, so that rather than acting as natural carbon sinks, they start to release carbon. Peatlands actually store about five times more carbon than forests (across Europe). Read more...
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...