The question to be answered is...
How can farmers use Short Rotation Cropping (SRC) of Willow (Salix genus) to increase Biodiversity and also to reduce our dependence on fossil fuels?
This project will introduce the changing values of willow over time, to both humans and non-humans. It will explore a principle concept of the O.U. U216 course:- that of instrumental, non-instrumental and intrinsic (or deep) values.
Change in perception of Willow values may continue in the 21st century with the Short Rotation Cropping (SRC) providing a renewable fuel that could also enhance biodiversity when grown as an alternative arable crop.
An observation and recording of the flowering dates of native willow will be made to confirm the availability of nectar and especially pollen in early spring. The life cycle of pollinating insects will be described to explain the need for pollen at this time.
The value of willow as the basis of an important food web for soil organisms, bacteria detritivores, invertebrates, insects, small mammals, birds, and larger predatory raptors will be demonstrated.
Historic values of willow from the 18th to 20th centuries will be chronicled to complete the picture and anticipate future values that may be both instrumentally and non-instrumentally beneficial to humans and to the environment.
Willow (Salix species) CHANGING VALUES
|Dates|| ||Quotes|| ||Uasage and Value|
Pre Ice Age
17 c John Evelyn Timber /fencing
early 19 c Culpepper Herbal medicine
early 20 c Elton Ecology
20 c Newsholme Horticulture
Sir Nicholas Stern
21c Biomass SRC
Willow certainly predates the arrival of humans on earth. Newsholme states that pollen grains and leaf fragments from Artic species growing in the Cretaceous period have been found by geologists. When the ice retreated after the last Ice Age, Artic Willows (Salix repens) were some of the first pioneer plants; it was these plants, which started the succession of land flora and fauna that we now enjoy.
. (Newsholme .C. 1992)
John Evelyn (Fig 1) as early as 1664 was commissioned by King Charles II to study the loss of the Royal forests and advise methods for regenerating and replanting them. His book 'Sylva' included Willow, native Salix varieties. These were grown for their quick regeneration after being coppiced or pollarded. He advised on methods of propagation, of pollarding, and coppicing and the maintenance of a continued supply of willow stakes, for use as tool handles, fences, vine supports and baskets. In his book 'Sylva' (Chapter 21: 8) He remarks of Willow "If some be permitted to wear their tops five or six years, their Palms will be very ample, and yield the first, and most plentiful relief to Bees, even before our Abricots blossom.' (Evelyn.J 1664)
Evelyn, realised that 'the tops' i.e. the blossom was valuable to the bees, but he may not have realised why that was so. He saw instrumental and non- instrumental
values in the plant itself, and the production of honey was also of benefit.
In the nineteenth century Culpepper (1826) the famous herbalist in his book
'Complete herbal & English Physician' writes about Willow herbal cures, many of them precursors of medicines used today
We can understand the non- instrumental value of pollen to the pollinating insects by studying the life cycle of the Honey Bee. (Fig 2 )
The life cycle of the group of insects, which pollinate willow blossom, is known as Complete Metamorphosis. The queen lays an egg into a specially constructed cell. It hatches in three days and the developing larva is first fed royal jelly that the workers derive from pollen. Pollen contains the vitamins, and proteins necessary for growth and development of the Pupa (chrysalis)
See Fig 2 - Life History of the Apis mellifera (honey bee)
need for pollen Egg Input of pollen by nurse
by young bees bees
During the first 5 or 6 days of adult life worker bees consume large
amounts of pollen to obtain the protein and amino acids needed for
their growth and final development. Thereafter the
bees require carbohydrate for energy. (Cushman. D 2007)
Fig 3 Photo of Honey Bee (Apis mellifera ) collecting pollen from Salix ( HooperT,1976)
The author's method was to observe local identified willows from January 2007. Table 1 shows the dates the willows were observed to have pollen, the date the flower lost it's pollen, and to draw a bar graph to show the availability of blossom to pollinating insects. See Graph 1
Table 1. Observation of the flowering dates of native UK willows 2007
Willow Start of flowering Finish flowering Days in flower
S.caprea (male) Jan 29 Feb 12 15 days
S..lanata (female) Feb 25 March 17 20 days
S. cinerea (male) Mar 16 April 1 16 days
S.fragilis (male) Mar 28 April 7 10 days
S alba (male) Apr 1 April 17 16 days
S viminalis (male) Apr 6 April 17 11 days
S sachaliensis Sekka (female) Mar 4 Mar 26 22days
From the Table 1 it can be clearly seen that in springtime, pollen will be available for the workers to collect, in order for the queen to build a successful colony.Willow is dioecious ie: individual plants are either male or female and thus pollen (the male gamete) will only be supplied by male plants of willow.
This is shown graphically in Graph 1 below
Fig 4 showing mature hedge of Salix caprea in full blossom Jan 29.07.07 (photo SMB)
jan feb feb feb mar mar mar mar apr apr apr
29 12 25 04 16 17 26/27 01 06/07 17
S.caprea S.lanata S.cinerea S.alba
Graph 1 to represent the period when pollen is available on male Salix varieties
In 18th and 19th centuries there was no apparent recognition of Willow trees for its value to wildlife. Evelyn and Culpepper were writing about willow, but it was for the tree's instrumental value to man, although both these writers appear to derive a spiritual element to their love of willows, an intrinsic value.
In the early 20th century, with the technological invention of the microscope, scientists (enabled to see micro-organisms for the first time) began to study the inter-relationships and energy flows between species. Charles Sutherland Elton named this new science 'Ecology' (Elton. Charles, Sutherland 1949)
Willow provides a very diverse habitat, second only to the native oak.
'Canolfan Faes' -Wales Biomass Centre (Web Site accessed July 25) states that Willow supports:
Table 2 Species supported by Willow Salix10 species mammals 151 species flora32 species birds 135 species invertebrates in the canopyand almost as many species of invertebrates in the rhizosphere.
Figure 5 (Author 2007) to show pyramid of numbers and ecology of a Willow Tree
Figure 5 shows the relationship between the autotroph, Willow Tree that photosynthesizes to produce food for a web of interdependent species, carnivores and herbivores, detritivores, fungi and bacteria.
All the above values are enjoyed today, both instrumentally and non-instrumentally, but industrialization has been damaging the environment; and in the late 20-century serious concerns about Climate Change, resulted in The Kyoto Protocol (1997), when eventually 141 countries agreed to a mandatory reduction in Green House Gas emissions, which were damaging the Ozone Layer. These gases mainly CO2 and CH4 (carbon dioxide and methane) are mainly anthropological emissions. (Success was achieved by banning CFC (Chlorofluorocarbons) at the Montreal Protocol. (1987). Emissions need to be drastically reduced, and attention has turned to the use of alternative Renewable Energy Sources - Wind power, Hydro Electric power and biomass use. This includes SRC Willow for production of Heat and Power.
The rapid growth of coppiced willow makes it ideal as a renewable fuel source.
Short Rotation Cropping (SRC) is a method used to produce renewable energy from fast growing tree species such as willow. Trees are planted at a high density and harvested on a short rotation (3-4 years). This method of fuel production is Carbon neutral, as the CO 2 released has previously been removed from the air during the growing of the crop. (Photosynthesis: 6CO2+ 12 H20 + sunlight = 2 C6 H12 O6 (biomass) + 6O2 oxygen
When exploring the potential benefits of SRC willow the author of this project found no farmers growing SRC willow locally.
However Thames Valley Bioenergy Group working for Oxfordshire County Council has started small initiatives in commercial SRC that they are overseeing for Slough Heat and Power. (Alker.Gillian Dr 2007)
Slough Heat and Power is part of Thames Valley Energy, committed to growing biomass alternatives. This field is owned by Oxfordshire County Council and is growing coppice Willow to be harvested and used to heat Shortenills Primary School. It had the first cut
Figure 6 Field at Kidlington Oxford. Map Ref FP 499121 (author's photo)
in winter 2007 and will now be grown on for three more years before being harvested.
At that time the Willow will be expected to be yield about 10 od tonnes / ha (oven-dried tonnes/fuel per hectare) It can continue being harvested every two or three years for up to twenty years.
Also in Berkshire, in Windsor Great Park area, Dinton Pastures Country Park.
carries out coppicing and pollarding by the rangers as part of an education programme about renewable energy. Schoolrooms are available for primary School children, to be taught the values of supplementing fossil fuels. Fig 7 Willow coppice -Height after three years (Author's photo SMB}. They are also taught willow crafts, and the values of willow as a diverse habitat.
The Biomass Task Force under Sir Ben Gill, reported in 2005, on the progress of the Energy Crops Scheme; that there was a lack of knowledge of the techniques required for this type of arable farming.
There was a "no targets, no concerted policy, no strategy and limited support for development." aspect There was a fragmented approach with the farmers, dti (Department of Trade and Industry), DEFRA, Forestry Commission, local planning committees and perhaps most resistant of all, the Electricity Suppliers operating from different perspectives. Problems with the supply chains and the available markets had been identified. The principle lesson is that action must be taken now if farmers are to contribute to efforts to reduce Carbon emissions. The findings were accepted by the Government, who set up The Biomass Energy Centre to coordinate information acting as a link for all parties involved. (Gill, Ben Sir, HM Treasury Web Site 2006)
Sir Nicholas Stern FBA,Senior Vice-President of the World Bank 2000-2003 , and now - Economic Adviser to U.K. Government on the economics of climate change and development, gave his Review on the Economics of Climate Change in October 30th 2006 to Prime Minister , Tony Blair.
He stated :
"Whatever approach is taken, the key aim of climate-change policy should be to ensure that those generating GHGs (green house gases) wherever they may be, face a marginal cost of emissions that reflects the damage they cause. This encourages emitters to invest in alternative, low-carbon technologies," (The Stern Review on Climate change from DEFRA website)
His Review stressed the need for quick action to reduce greenhouse gases and avoid the worst impacts of climate change. The government has since announced a target of 60% reduction in CO 2 by 2050.
There have been many recognized values for Willow species since the last Ice Age for humans and other species. Today's greatest challenge is to use willow to supplement fossil fuel use. This has been successful in Sweden and 1% of that country's heating fuel is produced this way, yielding about 200GWh from 2.500 hectares (SRC in Sweden Web Site accessed May 2007). Defra estimate that 1,000,000 hectares may be available for total biomass in UK.
Research by both Defra and Forestry commission has demonstrated the excellent increase in diversity when SRC crops are planted, which could increase even more if male 'pollen producing plants ' were grown.
The Government's Sustainable Energy Policy is based on 60% reduction of CO2 emissions by 2050 and following research to evaluate any unacceptable effects from a change in farming practice; SRC Willow could be a significant contributor.
Many environmental problems can only be solved by accepting compromise and taking care to achieve a balance between economic considerations and environmental concerns. The government's Energy Crops Scheme may not convince farmers who have been asked to 'Set Aside', attract tourism, and accept impossible competition from foreign imports, that they will be treated fairly when asked to produce fuel rather than food. They will have 'unfamiliar crops seeking unknown markets 'and a fragmented approach with too many organizations involved, all trying to balance economics and environmental issues.
Fig 8 Harvesting SRC willow
Globally other values have been recognized for Willow. It has been used for its dense root system to stabilize river and canal banks. It has been used to extract heavy metal pollutants into its tissues to detoxify soils (phytoextraction). The Dutch use it as a barrier along their 'Motorway system' to absorb noise and provide a more attractive screen than concrete. It is proven to have great value. .2119 -63 = 2056