Miskantu un īscirtmeta kārklu plantāciju ierīkošanas iespēju salīdzinājums Velsā

Jan 9 2007

"Agriculture is entering a period of change. New crops such as miscanthus and short rotation willow coppice (SRC) are set to change cropping patterns and open up a new energy market to growers and the wider rural community.
As custodians of the environment, the choices that farmers and landowners make have direct implications, both positive and negative, for the rest of us.
There is now no doubt that our climate is changing, and there are two ways in which we can respond. The first is through mitigation – reducing greenhouse gas emissions – and the second is through adaptation – responding to the impacts of climate change.
Mitigating actions include changing the way we farm, by reducing carbon emissions, for example, and by replacing processes that emit greenhouse gases with carbon neutral energy sources. Biomass crops such as miscanthus and SRC fall into this category.
Biomass crops are widely regarded as almost carbon-neutral because the carbon dioxide released when these crops are burnt as a fuel for heat or for electricity is matched by the amount of carbon dioxide the plants absorbed through photosynthesis when they were growing. As a fuel, therefore, they are substantially more environmentally friendly than fossil fuels.
However, this doesn’t give us the full picture. The way the crops are grown, the land use they replace and biodiversity all need to be considered for a good understanding of the environmental impact of introducing these crops into the Welsh landscape.
Wales is predominantly agricultural with roughly 74% of the total land area – 1,629,000 hectares or just over four million acres – classified as agricultural. Of this, 85% is permanent pasture or rough grazing, 11% is arable and the remaining 4% is woodland or set-aside.
Miscanthus and SRC are both long-term perennial crops. Miscanthus originated in Asia and the current commercial variety miscanthus x giganteus is a sterile hybrid that does not produce seed. It is a fast-growing, clump- forming, non- invasive grass, a long-term perennial crop with a potential productive life of some 20 years.
Many willow species are native to Britain where they have been part of the landscape for hundreds of years. Willow (salix.spp.) is a diverse species, with several hundred varieties readily available within Wales.
The osier or basket willow salix viminalis is a shrub native to the UK and it is the parental stock to many of the willow varieties planted for use as short rotation coppice. Its production is more comparable to agricultural cropping methods than it is to forestry.
Both crops are planted in the spring, miscanthus as rhizomes and SRC as rods. Weed control is essential during the establishment phases (years 1 and 2) and herbicides are routinely used.
Trials in upland areas of Wales suggest fertiliser applications may be beneficial and the addition of lime is likely to be essential in these areas. Using organic wastes such as cattle slurry or treated sewage sludge can reduce the environmental impact compared to inorganic fertiliser applications.
As the crops approach harvest they translocate nutrients, back into the rhizomes in the case of miscanthus, or into the stools in the case of SRC.
Leaves drop in the winter adding organic matter and increasing soil nutrient status. Both crops have much lower agricultural inputs than conventional arable crops and the risk of ground water contamination by agro- chemicals is very low.
There are currently no pests and diseases in miscanthus, but SRC crops attract a lot of invertebrates and the crop is susceptible to a number of insect pests, particularly willow beetles, which can cause considerable damage. The crop is also susceptible to diseases, the most important of which is rust.
But the need for insecticides to control pests and disease can be minimised by careful plantation design and varietal selection. Varieties are now being bred with resistance to pests and diseases in an effort to reduce dependence on fungicides and insecticides.
Both crops have a good root system and well-developed mechanisms for recycling mineral nutrients. They can be used as buffers along rivers, blocking surface run-off and phosphorus pollution, particularly at the bottom of slopes. As the crops are perennial, soil disturbance is reduced with the potentially damaging effect of yearly soil cultivations being avoided.
The roots help bind soil together, stabilising it and reducing the risk of soil erosion. Both crops use a large amount of water and SRC is deep rooting and can damage land drains. SRC will grow well on most land where there is a reasonable level of rainfall and is therefore well suited to the Welsh climate.
Miscanthus and SRC are fast growing, tall crops that can radically change the appearance of a site so it is important to consider the site’s ecological and historical value as well as the visual impact of the crop on the landscape. For this reason it is currently a requirement that those proposing to grow SRC complete an environmental statement provided by the Forestry Commission. This will then determine whether a full Environmental Impact Assessment (EIA) is required.
Replacement of grassland with biomass crops may have greater environmental implications. With 85% of Welsh agricultural land under grass this is likely to be particularly an issue in Wales.
Ploughing up long-term grassland releases large amounts of carbon to the atmosphere and this adversely affects the greenhouse gas abatement objective of biomass production. But there is a big difference between replacing a 50-year-old species rich meadow, and replacing a three-year-old intensively managed rotational grass crop, for example.
Energy grass crops can be grown on set-aside land and can make farmers useful additional income in the process.
Transport also needs to be taken into account. In order to be both economically and environmentally viable, crops need to be grown close to where they will be used as a fuel.
Good planning and management practices include avoiding priority habitats and untouched wildlife niches, and minimal use of insecticides and herbicides. These measures alone can go a long way to ensuring that biodiversity is maintained or increased over previous land use. In addition, the crops need to be part of a mix of farming land use.
Energy crops can create new habitats and opportunities for colonisation by many species of plants and animals. SRC has been found to be particularly species diverse, with three times as many invertebrates as cereal crops and a higher density and more species of birds – although it is potentially detrimental to some species that prefer a more open habitat.
Fewer bird species are found in miscanthus crops, though young crops of miscanthus offer patches of bare ground that are popular with birds such as skylarks and lapwings, and the crop offers a good over-wintering habitat.
Both SRC and miscanthus are harvested in winter, which is outside breeding times and summer migrants are not present. Two-to- three-year-old miscanthus plantations are used as over-wintering sites for birds, small mammals and invertebrates.
So it would appear that younger crops of both SRC and miscanthus have a higher level of biodiversity than older, fully established crops.
Of the two, willow can be seen as being richer in biodiversity terms, with miscanthus having biodiversity levels more comparable to arable crops, though with the added bonus of no insecticide and fertiliser requirements.
Properly planned SRC and miscanthus plantations can enhance the landscape and environment, reduce our dependence on fossil fuels and bring new markets to the rural economy.
Farmers are the custodians of the environment and keeping them in business is key to keeping our rural heritage alive."