Course notes / Unit 2

Salt marshes

Where a coast is sheltered from heavy waves, mud collects and grasses take hold. The result is a salt marsh, flooded by the tide and drained again every day.

Plants in stripes

Marsh plants sort themselves by how often they are flooded and how much salt they can handle. Tall cordgrass grows at the muddy seaward edge, where the tide reaches daily. Glasswort, a fleshy green plant, fills the middle. Higher up, where only the biggest tides arrive, finer grasses and flowers such as sea lavender appear.

What a marsh does

• Nursery. Young fish and crabs shelter among the stems while they grow.
• Filter. Slow water drops its mud, and plants take up some of the nutrients washed off the land.
• Cushion. Dense stems slow waves and lower their energy before they reach the land behind.
• Store. Waterlogged soil breaks plant matter down very slowly, so carbon stays locked in the mud.

Pressures

Marshes need room to move inland as the sea rises. Sea walls, drained farmland and roads can leave them squeezed with nowhere to go. Too many nutrients from the land can also change which plants thrive.

Field exercise

Walk from the water’s edge toward the land and note where the plant type changes. Draw a simple strip map with each band labelled and a rough guess at its width.