We recently went on one of our intermittent winter seaweed scavenges, in order to re-build our compost and manure piles ready for spring. Our supply of seaweed is important during spring for our potato beds; we cover them in winter (Nov/Dec) and leave the seaweed to rot down, then plant through any remaining, which then gets covered with compost or soil as we earth up the growing plants. It’s also important for our rhubarb and our asparagus beds, as well as valuable addition to our compost piles, and liquid fertiliser for our courgettes and pumpkins. We use seaweed in place of horse or cow manure to avoid the possibility of amino/clopyralid contamination and potential devastation for our allotment, something that has happened to many allotment holders on our site and across the city.
Winter along the south coast can be surprisingly stormy, and generally we’re assured of good supplies of seaweed during these months. Several days after stormy seas the seaweed harvest usually starts arriving on the shore. This year there’s been very little evidence of this. There are large seaweed beds off the coast at Bognor Regis, which provide the supply of Laminaria during the winter, one of the best seaweeds for mineral content. The Seaweed beds off Bognor are to the SW of Brighton, and the seaborne seaweed is moved along the coast through the process of longshore drift. The prevailing winds are from the SW, and the line of travel for longshore drift is also W-E. Hence, stormy seas tear seaweed from the seabed to the West of us, longshore drift transports the seaweed W-E along the coast then deposits it on the beaches, nearby. This year, the lack of seaweed suggests something else is happening.
Our current cold weather across the UK is caused by a weather system over the near continent. High pressure between Iceland and Norway has led to winds blowing East-West, from the high pressure to the north of us towards the low pressure to the west of the British Isles out in the Atlantic – remember ‘Winds blow from high to low’. So, I reckon, the winds have been blowing in the opposite direction to usual during winter, while longshore drift continues its movement West-East. This, I think has led to storm-torn seaweed clusters not moving inshore, but remaining suspended off-shore; the winds blowing from the East and longshore drift acting from the West has created an equilibrium. Hence, the distinct absence of seaweed this winter.
Such a small shift in our weather patterns, yet it could have a significant effect on our crops and harvests this year; I reckon we need to do some research.