December 14, 2022 0 Comments

Bankside trees provide a mature aesthetic that creates a sheltered angling environment which we all prefer to fish in. When we highlight the hinderance of these trees on the aquatic ecosystem, we’re often met with the argument that our management plan destroys that mature feel.

Let’s start with why sunlight is so important, the sun is a crucial element of the nitrogen cycle which is required to allow plants and algae to photosynthesise. It’s this photosynthesis process that’s needed to absorb the nitrates produced by the nitrogen cycle. 

Limiting the sunlight allows the nitrogen to build up without sufficient absorption from plants, algae and weed. This build up of food for the algae can create a situation where the algae can bloom aggressively. This algae bloom can become so successful in exploiting this nitrogen opportunity that they quickly exhaust the supply causing the algae cells to die. Oxygen will crash very quickly in these circumstances because aerobic bacteria are extremely reactive in processing these single dead algae cells, in doing so they demand oxygen and therefore quickly exhaust the dissolved oxygen supplies in the water. 

Allowing UV energy to reach the water ensures consistent photosynthesis to keep those nitrate levels controlled, reducing the risk of opportunistic algae blooms which thriver and dive.

The Sunlight is also carrying valuable heat energy which the trees on the southern and westerly banks will intercept and absorb to grow. We want the water to absorb this heat energy! The temperature contrast between sunlight and shade might only be 1 or 2 degrees, which don’t make much of a difference in a day or a week, but those degrees hours over a year all accumulate and contribute substantially to the 10 year growth trajectory of a fishery.

Temperature’s not only key to the efficiency of the digestive enzymes related to fish growth, but also another crucial element to the nitrogen cycle. The warmer the water, the faster the bacteria will reproduce and recycle organic debris into the food chain.

So we’ve briefly explained the importance of the sun and how trees compromise the organic recycling process, but trees not only hinder the efficiency of the nitrogen cycle, they’re also the main contributors of organic litter entering that very same cycle! Imagine the tonnes of leaves deposited into the water every year from these trees, you’re going to need a very efficient nitrogen cycle to process that lot! 

So if the sun travels from East to West, it’s the southern to westerly trees that block the strongest hours of sunlight. Now think about all the leaf contribution from these trees! 

The prevailing winds that sweep across the UK more often than not come from the south west. Therefore, the leaves and branches from the trees on the south west banks will most likely all end up deposited into the water.

We would ideally up-root bankside trees where practical and replace that space with marginal plants like Carex which absorb nitrogen without stealing that all important sunlight required to work its magic on the ecosystem. Every daylight hour of sunlight counts!