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| Cost Effective Landscape: Learning from Nature |
| Part 3: Specify detail |
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Vegetation diversity Specify detail - use natural characteristics Providing conditions that put plants under stress reduces competition between species. Reduced competition leads to increased species diversity. Competitive plants are encouraged by fertile soils and while grass growth is vigorous, plant diversity is reduced. Persistent and vigorous grass growth will suppress the process of natural succession to scrub and provide a habitat for small mammals like mice and voles. Vigorous grass growth can therefore be used positively to prevent succession to scrub where it is not required. Clover enriches the nitrogen level of soil. This enhancement of fertility discourages plant diversity. Clover should therefore only be used where vigorous and persistent grass growth is required. Creating the right conditions and specifying the right plants for particular conditions to meet well considered landscape objectives is a fundamental principle of the policy. An understanding of the relationship between geology, soils and vegetation will enable this principle to be used positively. Reduced competition - increased species diversity Clover promotes vigorous grass growth Native species Use natural characteristics - ecological potential In 1994 various improvements to the A830 trunk road from Fort William to Mallaig were being planned. To help preserve and enhance the purity of the biodiversity in the West Highlands an advance contract was let to grow the trees required for the works. The seed was collected in the vicinity from trees of known origin. Planting trees of local origin, especially pine, oak and birch in the more extreme locations can also give best value for money. Invertebrates and Reptiles Use natural characteristics - ecological potential Open habitats such as these on south facing slopes, are excellent for invertebrates and reptiles. These habitats are frequently disregarded or undervalued and opportunities should be sought to create or preserve open areas to enhance biodiversity.
The traditional approach Exploration of solutions - using natural characteristics. This area of planting on an embankment of the A1 has been designed and implemented to a high standard using traditional methods and techniques. This approach will produce, in time, a valuable area of vegetation. It is important that the design process should assess the benefits of using alternative methods as they may result in an improved product with a higher landscape and ecological value, cost and time benefits. The traditional regular spacing design has established well during its first year and will develop natural characteristics if allowed to grow without unnecessary routine maintenance or intervention. Some trees will die some will grow better than others. Scrub will invade and wildlife will move in. The tree shelters and stakes could be removed next spring and be recycled. By learning from nature, observing and understanding how plants colonise and thrive, alternative methods can be proposed which may be better suited to achieving the required objectives. For example; the natural variation of the site should be taken into consideration with species suited to freer draining conditions at the top of the slopes and those suited to the flushed conditions below. Areas could be left open to naturally regenerate and shade tolerant shrub species could be mixed with canopy species to create diversity of structure. Ways of achieving a more natural spacing could be explored. Whether you look down or up, nature can inspire: "templates for design". The Great Storm 1987 Use natural characteristics In October 1987 a storm swept across the south of England and blew approximately 15 million trees down. In most cases fallen trees were cleared from woodlands and young trees replanted. Millions of pounds of public money was spent. Some woodlands were left alone and allowed to regenerate naturally. Subsequent studies of both approaches2have concluded that in some cases more damage was done by well-intentioned clearing up and replanting than by the storm itself; the woodlands that were left to their own devices have recovered best. This evidence reaffirms that by working with nature, economic and environmental benefits can be complementary. Ecology is of course only one consideration. Direct action, within the framework of this policy, will normally be required to remedy destruction of landscape character, commercial forestry and amenity planting.
2 Reports by Kent and Sussex Wildlife Trust. Woodland fungi, East Lothian. 1997 Wood boring beetle larva. 1996 Landscape character Explore alternatives - use natural characteristics The attention to design detail and aesthetic quality of these culverts has declined as road building technology has improved. Sympathetic and sustainable devel-opment can only be achieved with an understanding of natural and man made vernacular character and paying particular attention to detail. In the scale and grandeur of the west highland landscape the small scale detail can sometimes be overlooked. Culvert for General Wades Military Road Culvert for A87 Glen Shiel circa 1930 Culvert for otter passage. 1995 No peat - no growth! Use natural characteristics - objectives changed. The rock cutting in the top two photographs was formed in 1994. A landscape architect worked closely with the engineer throughout the design and construction process. Together they introduced natural characteristics of indigenous rock outcrops to the basic form of the cutting. No peat/soil was placed on the berm on the grounds that it would impede access for inspection and future maintenance operations. Consequently, little vegetation has developed and the rock cutting has not integrated well with its surroundings. This approach would question the general presumption against not placing peat/soil on the berm and also over the drain at the foot of the cutting. As a result of this evidence, peat/soil has now been placed on new rock cuttings on the A830. Exposed rock. Some peat - some growth! Use natural characteristics The rock cutting in the top photograph has the potential to develop natural rock characteristics similar to the outcrop in the distance. It will only do so if vegetation develops in places where organic matter would naturally occur. To hasten this process of regeneration, peat/soil has been placed on the cutting slope so that it cascades down the rock face to lodge naturally in the niches and ledges as illustrated in the smaller rock cut below. (see previous page). It is important that the peat/soil is generated from the construction site and not imported from elsewhere. Wildlife culverts Use natural characteristics - explore alternatives Natural characteristics have been ignored in the design of the entrance to this otter pass. The white concrete is unsympathetic to the natural landscape in terms of colour, form, smell and texture and it is likely that it contributes little in encouraging wild animals to enter. By studying the surrounding landscape and otter holts in the vicinity, clues could be discovered, which if applied in the design process, could produce a more successful product. For example the top right photograph illustrates a natural holt near by. NRD will undertake a monitoring exercise to study the behaviour of otters in relation to the use of these tunnels with a view to improving the performance of these underpasses and wildlife underpasses elsewhere. Soils Use natural characteristics-
management commitment - ecological potential. Creating the conditions to encourage the required effect leads to sustainable results. Low soil fertility created through a low level of nutrients or thin soils promotes a high diversity of non-competitive plant species which in turn reduces routine maintenance costs and enhances amenity. In this example 35-50 mm of topsoil is being placed on side slopes as the contract requires to provide just enough soil for grass establishment and to sustain adequate growth. A greater depth would promote and sustain unnecessarily vigorous growth. A1, Tranent - Haddington. 1997 Diverse ground conditions Natural characteristics - ecological potential Diverse ground conditions are the foundation for diverse vegetation Diverse vegetation promotes rich biodiversity. In these examples on the left, ground conditions were created to encourage spontaneous growth of diverse and attractive vegetation at very little cost. The specification of an even layer of topsoil is generally not appropriate or necessary where a landscape natural in appearance is required. Nature rarely provides an homogeneous topsoil layer, especially on slopes. Designers should reflect this characteristic where appropriate. Substantial cost savings may be possible during the implementation period, as specifying diverse ground conditions allows unforeseen shortfalls or surpluses of excavated material to be dealt with positively. Regeneration Use natural characteristics. The vegetation patterns and rationale for natural regeneration should be observed, understood and utilised where appropriate. Peat was deposited and retained on this embankment. Natural regeneration of birch and heather then occurred through seeds in the soil and seed transfer from the adjacent woodland. The vegetation cover subsequently developed without assistance. This establishment technique is extremely successful in certain situations, namely where local peat is available and where a seed source is adjacent. Much can be learned from studying natural vegetation patterns of any description. For example in the above photographs the following characteristics are apparent:
These characteristics are rarely duplicated in designed planting schemes. Designers should assess their merits of natural characteristics and utilise them where ever possible. Integration Use natural characteristics If the landscape objective is to integrate the new with the existing landscape then the natural characteristics of that location must be understood and utilised. This project implemented 12 individual diversions of the Evan Water near Moffat. The rock armoured banks required to protect the adjacent road do not integrate well with the existing landscape because the natural characteristics have not been understood and used. For example, by studying and copying the detail of the existing riparian vegetation pattern, a more natural looking landscape with greater ecological potential would have resulted. This could be achieved by placing and containing soils within the banks to allow vegetation growth, limited planting and varying the rock placement. Creating the right conditions Use natural characteristics - ecological potential. By promoting natural processes, landscapes can be created which are self reliant and diverse. In 1985, 77,000 m3 of peat were placed on these embankment slopes to create the conditions to stimulate spontaneous vegetation growth. A thin layer of topsoil was placed on the level verge and behind the safety barrier to support a grass cover.
By 1989 a clear pattern of vegetation had appeared, directly related to the soil conditions. Creating the correct ground conditions is the most important single criteria to promote sustainable vegetation and 'Bottom Dead Centre' designs. There will always be lessons to learn by observation and study of established landscape where ever it is. The first is to develop a habit of looking, seeing and questioning the rationale the second is to develop further our skills in applying natural processes imaginatively to meet our needs. The central reserve Use natural characteristics - wise use of resources. Seeding in the central reserve of rural roads has the following benefits;
Dried grass in the winter and early spring turns yellow and can highlight the central reserve especially during hours of darkness. This can contribute to road safety. The growth rate of grass and the need for routine grass cutting in the central reserve can be reduced by providing a low fertility, shallow depth of topsoil or sand there. Right plant right place Use natural characteristics - wise use of resources - management commitment. Vegetation has a relentless desire to grow in central reservations. Attempting to prevent spontaneous growth is never ending, costly, hazardous, makes unwise use of energy and resources and is not sustainable. The policy requires alternative approaches to be generated and assessed to find a more sustainable approach. For example a type of vegetation could be established which could co-exist with the functional requirements of the highway and require little or no routine maintenance. The spontaneous growth of hawkweed on the M9 indicates that it can tolerate and may even thrive in the harsh central reserve conditions. A mixture of hawkweed and other wild grasses could possibly provide a sustainable solution. The verge Wise use of resources - use natural characteristics. This roadside landscape has developed from infertile soil conditions and infrequent, grass cutting for safety reasons. The wildflowers were not seeded. The sward has developed naturally at no cost. Because the wildflowers have arrived spontaneously it is likely that they find the conditions favourable to their well being and as long as this remains the case they will be relatively self-sustaining. The low frequency of functional grass cutting provides the right regime for preventing colonisation by scrub and for retaining the species diversity. It is important to understand that the variables in nature are infinite and that predictability will depend on knowledge, skill and understanding. Establishment period Assess maintenance requirements. Landscape, like any living organism or system, requires nurturing in the early years to be successful and become self-reliant. The length of this period of intensive care is dependent on several factors including;
The designer must understand the site specific factors which contribute to self-reliant landscape, monitor establishment and tailor the length of the establishment period accordingly. |
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