Trading Ecosystems: the ecological implications of marsh conversion

Graham R. Daborn

Symposium on the Protection of Agricultural Heritage

Acadia University17 April 2010

““Henceforth thou art the Genius of the shore,Henceforth thou art the Genius of the shore,In thy large recompense, and shalt be goodIn thy large recompense, and shalt be goodTo all that wander in that perilous flood.”To all that wander in that perilous flood.”

John Milton John Milton Lycidas (1638) L. 182-185.

Sherman Bleakney

The Bay of Fundy is continually changing

Pre-1604• > 100,000

acres of marsh

Morris Map 1724

Arrival of the Acadians

• First dykes constructed at Port Royal 1635-1640

Acadian Conversions to1755

• By 1755 many thousands of acres of alt marsh had been dyked in the areas of Annapolis, Grand Pré, Truro, Beaubassin, Missiguash, Shepody, Tantramar etc.

Acadian uses of dyked lands

• A great variety of crops were raised:hay, wheat, peas, oats, barley, corn, carrots, beets, parsnips, onions, chives, cabbage, turnips etc.

Post-1755 history• With the Expulsion, marsh conversion did not

stop; the Planters took over.• NS 1760 “Act for Appointing Commissioners of

Sewers” included

“Whereas great quantities of marsh, meadows and low ground…are spoiled by overflowing of the sea…the new settlers…be encouraged…to raise dykes and remove such obstructions as prevent these lands from being immediately useful;..”

19th & 20th centuries• Wellington Dyke #1 1816-1823• Aulac 1825• Saxby Gale 1869• Maritime Dykeland Rehabilitation Committee

1943• Habitant Aboiteau 1944• Wellington Dyke #2 • Maritime Marshlands Rehabilitation Act 1949

Does it matter?

Fundy Marshes• A rich, low diversity

plant association dominated by Spartina patens (marsh hay),

• Spartina alterniflora (marsh cord grass), Juncus spp., Limonium spp. (sea lavender) etc.

Animals of the marsh

Animals of the marsh

Fundy Marshes in Summer

Fundy in Winter

Are Fundy salt marshes stable?

Fort Anne• Shoreline

erosion exposed timbers laid down in 1740s

1955Limit of marsh

1992

1996

2003

Windsor Causeway

(1970)

Grande Pre

Windsor

1200

Annual production of S. alterniflora marshes in North America

Fundy Salt Marshes

Conclusion• Fundy salt marshes are among the most

productive in North America.• Fundy salt marshes act as ‘soft’ shoreline

defenses, constantly adjusting to sea level rise.• If ‘let out to sea’, dyked lands will take a long

time to recover their original function: therefore, if they are used productively, there may be no net benefit to removing the dykes.

• If not used productively, why not return them?

“…..take heed lest passion swayThy judgement to do aught which else free-willWould not admit;….”

John Milton ‘Paradise Lost’ VIII:635-637.