Outline the challenges and opportunities for human activity in present peri-glacial environments
The term peri-glacial means near to or on the fringe of an ice-sheet. This term is however more widely used to include any area that has a cold climate or areas that have experienced severe frost action in the past. Today the main peri-glacial areas are in the artic regions of Canada, USA and Russia. Frost and snow have a major impact on the landscape in these areas hence resulting in potential opportunities and in some cases, challenges. Peri-glacial areas can be further inhibited as they are characterised by a layer of permafrost or permanently frozen ground.
Peri-glacial areas present many problems for settlements and therefore it is logical that most peri-glacial areas are sparsely populated and largely underdeveloped. This climate has six months of long, dark and very cold winters, with temperatures staying well below freezing for almost half of the year. During the short summer the temperatures are warm enough for plants to grow. People who live in this area rely on caribou, fish and marine mammals for food. Water in the soil below the surface remains frozen throughout the year therefore vegetation growth is minimal and limited to only mosses, lichens and low shrubs.
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Water is unable to drain through the permafrost and therefore the land remains wet. This is however good as the wet areas support large numbers of insects and birds during the short summer months. A thermokarst is a good example of a peri-glacial environment where human activity influences the climatic equilibrium. Thermal equilibrium in a thermokarst may be upset by human occupancy and development; this will either increase or reduce the thermokarst. This can occur in a number of ways; an increase in the thermokarst means that the level of the permafrost table is lowered.
This can happen when vegetation is removed for construction purposes, in the summer more heat penetrates the soil and so the depth of thaw increases; this can be dangerous for settlements as the risk of flooding is increased. The level of permafrost can also be lowered by the construction of centrally heated buildings. This warms the ground underneath causing the buildings to subside. Construction of buildings is also difficult as the ground cannot be dug without the thermal equilibrium being affected and so foundations for the building cannot exist.
For this reason many of the buildings in peri-glacial areas are constructed on stilts, this also allows wind and snow to blow past the house without collecting around it and causing access in and out of the house to be difficult. Settlements in peri-glacial areas poses further problems as siting of oil, sewerage and water pipes in the active zone where they otherwise would be increases the rate of thaw. This causes fracturing of the pipes as the ground moves. Similar earth movements have caused roads and railways to lose alignment and dams and bridges to crack.
To combat this problem those living in permafrost areas have constructed an above-ground network of pipelines. The drilling for oils and gases that are often found in these landscapes also melts permafrost. The level of permafrost can alternatively be raised; this will also pose problems for settlements situated in the area. For example, the construction of unheated buildings can upset the thermal balance in the opposite direction as the low amounts of heat received during the short summer are further reduced, the upper surface of the permafrost rises and buildings can tilt.
Early road construction also caused the permafrost table to rise and large, modern unheated buildings and airstrips are constructed in thick gravel pads that are immune to frost heaving and have fewer tendencies to thaw the underlying permafrost. This has however been overcome as heat extractors can be installed to prevent to extension of the thermokarst. Transport for people living in these areas can also be a problem as route ways cannot be easily found due to the existence of blockfields and uneven, sloping land.
If the roads are formed they must then face problems of icing. If the area is to become flooded and this spreads over a cold, flat surface such as the road, freezing occurs and a sheet of ice forms which might accumulate to be several metres thick. This problem can however be overcome by lorries with steam generators. The construction and maintenance of roads therefore poses problems but if constructed can also prove advantageous as access is made easier to the outside world and particularly tourists from whom profit can be made.
Low temperatures, limited organic life and the lack of circulating ground waters are caused by peri-glacial environments and are in turn reflected in the character of tundra soils. This causes agricultural problems for the area as the impeded drainage affects about 90% of the tundra area; bog soils therefore occupy most of the area. Agriculture problems exist, as the growing season is very short at only three months, low temperatures for most of the year mean that there is little growth, soils are unstable, there is poor drainage, low rainfall and the soils are thin.
A peri-glacial environment is also a low-energy environment and so long periods of continuous night and low levels of sunlight means that photosynthesis is limited. Recycling of materials is also slow as plants lie dormant for most of the year and animals migrate or hibernate during the winter months, few nutrients are therefore being put into the soil. Land in peri-glacial environments is also subject to frost heave. Frost heave includes several processes which cause either fine-grained soils such as silts and clays to expand to form small domes, or individual stones within the soil to be moved to the surface.
This occurs because the thermal conductivity of stones is greater than that of soil. As a result, the area under a stone becomes colder than the surrounding soul, and ice crystals form. Further expansion by the ice widens the capillaries in the soil, allowing more moisture to rise and to freeze. The crystals or the larger ice lenses which form at a greater depth, force the stones above them to rise until eventually they reach the surface. Both of these processes make the land difficult to plough and to be cultivated, as stones would have to be constantly removed from the land to allow for plant growth.
The process of frost heave is shown in the diagram below: Frost weathering also occurs in these areas resulting in the formation of blockfields hence causing further problems for agriculture in the area. This occurs as mechanical weathering is far more significant in peri-glacial areas than chemical weathering, freeze-thaw being the main process. We can see examples of this and blockfields in the Scafell range in the Lake District and in the Glyders, Snowdonia. Blockfields consist of large, angular boulders, formed in situ by frost action. The impact of forestry on the peatlands is severe and destroys the unique flow ecosystem.
The deep ploughing and drainage which precede planting damage the vegetation, lower the water table and bring to a halt thousands of years of peat formation. Other effects go beyond the plantations themselves and include river siltation and the acidification of freshwater habitats through fertilisers. The introduction of tourism into a peri-glacial environment has many advantages as well as disadvantages. Whilst tourism may be very beneficial to the area in economic terms, the effects of tourism on the environment that come hand in hand with this are not quite so positive.
Employment generated by the tourist industry has meant that jobs are available locally where unemployment was before a big problem. Economic profit made can also be used to improve the area as it becomes more developed, better communications and infrastructure is needed that can benefit tourists and locals alike. There are however considerable disadvantages to tourism in peri-glacial areas as the tourists are attracted to the wilderness aspect of the area; increased numbers of visitors make a greater impact on these areas thereby making them less attractive as wilderness areas.
As the resort area becomes more and more popular further development of entirely new ski resorts and so on must be constructed in order to accommodate the visitors, new access roads, more uplift facilities, ski runs, restaurants and accommodation will also be needed, scarring the landscape further. Tourism therefore has a visual impact on the area as roads, pylons, snow fences and buildings intrude on the wilderness of the area. Other forms of recreation are also affected; field studies and hill walking for example are pushed out of the area and are no longer seen to be acceptable.
Quarrying for rock resources and drilling for oil also poses problems and advantages for human activity. Oil deposits and other natural resources found in the area cause fortune hunters to come to the area and bring much profit to the area as employment and resources are introduced to the area. Problems however arise when we consider the massive damage done to the environment and the scars that are left behind that might never heal.
Because the thermal equilibrium is so fragile it is near impossible that quarrying or drilling for oil would not affect this, this causes changes in the water table and perhaps flooding. The animals and plant life of the area is also affected as their habitat is destroyed, some species could possibly be made extinct. There are many opportunities and challenges to be considered for human activity in peri-glacial environments and it is essential that the both problems and benefits should be weighed up if sustainable development is to exist in these areas without the destruction of the environment.
Present peri-glacial environments are however not solely affected by those occupying the area. For example the effects of global warming might well be responsible for changes within the thermal equilibrium of the area as summer months become warmer hence causing the active layer to melt more rapidly, this could result in flooding and could prove a potential disaster for both those living in the area and those merely visiting it.