Posted by: Anne Murray | April 2, 2013

Boundary Bay’s sand dunes ~ a rare ecosystem

spit view 2 oct 31 06

Sand spit developing on Boundary Bay shore

Walk behind the South Delta Recreation Centre and you can sometimes see shells poking through the grass. The elevated ground here once marked the high tide mark at Beach Grove. A large midden, or ancient waste pile of discarded shells, dating back thousands of years, stretches across 16 Avenue and into the golf course. The ocean gradually retreated and new sediment was added, filling in the northwestern shore of Boundary Bay. The present beach is very dynamic, with new sand banks forming parallel to the shore and creating lagoons. Where houses abut the water in Beach Grove, very little sand dune remains, and the beach is mostly flat, whereas south of Boundary Bay regional park, there are more extensive areas of high, dry sand. Older dunes within the park have some interesting plant species and sand wasp colonies.

The provincial Ministry of Forests, Lands and Natural Resource Operations describe the sand dunes around Boundary Bay as rare and sensitive ecosystems. Staff recently undertook restoration work in Beach Grove, removing invasive plant species that have escaped from adjacent gardens. Within the regional park, many native and non-native plants grow on the sand dunes and in the salty, upper-tidal sand. One of the most striking in June and July is the saltmarsh dodder, whose tangled, orange stalks look like sprayed fluorescent paint or plastic string. It is parasitic on sea asparagus (Salicornia), has no roots and only stumps of leaves, and obtains its nutrients entirely from the host plant. The tiny white flowers are only visible on close inspection.

dodder 2

Saltmarsh dodder

Another strange plant is the big-headed sedge, which has brown spiky flowers and thin, grass-like leaves. It anchors the sand in place with its roots and helps stabilize the dunes. Female and male flowers (the former larger than the latter) are on different plants. Brilliant yellow flowers belong to the entire-leaved gumweed, a showy plant with sticky buds, at its best in mid-summer when it blooms in abundance. Sheep sorrel, a delicate, red-flowered plant, found on dry dunes, is one of many European plants that have infiltrated the delta over the years. Sea thrift, silver burweed, blue-eyed mary and Lomatium or Indian consumption plant are other sand-loving plants. Blue-eyed mary flowers in late March and early April. The seeds and leaves of Lomatium were a traditional herbal treatment for tuberculosis, also known as consumption. They taste of celery.

bigheaded sedge

Big-headed sedge

Boundary Bay’s special sand dunes are well worth a closer look; tread carefully!

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