West Coast Rainfall and Rainforests: Nature's Beauty

Whatever the location of your West Coast accommodation, two things are bound to be somewhere near you: rain and rainforest.

Although it’s a popular misconception that it rains all the time on the West Coast, without its drenching, life-bringing rains, “the Coast” (as locals call it) would be a very different place.  It’s hard to imagine Westland without its vast tracts of rainforest; and, indeed, if not for the bountiful forests, the early economy of this isolated and wild region of New Zealand might never have gotten off the ground. Today, of course, one of the main reasons people visit the “Wet Coat” (another local nickname) is to experience its majestic rainforests.  So here are some interesting facts about the rain and rainforests of the West Coast.

Orographic Rain

Rain is the life-blood of the ecosystems of Westland and its unique location, with a wide expanse of ocean on one side, and a sharply-rising mountain range on the other, means that rain, more than any other factor, has shaped both the geography and the natural history of the West Coast.  The strong westerly winds which blow across the Tasman Sea pick up water vapour from the surface of the ocean as they move.  When these moisture-laden air masses encounter the western side of the Southern Alps they are forced to rise.  A complex set of physical properties – including, among other things, the adiabatic lapse rate and the Dew Point (don’t worry, there won’t be a test later!) – causes the water vapour to condense out of the air in the form of rain.

And what rain!  On the West Coast it is measured not in millimetres but in metres.  The Cropp River, inland from Hokitika, receives eighteen metres of rain annually, making it the wettest place in New Zealand.  At higher altitudes, the rain falls as snow, filling the alpine basins and forming the glaciers which have shaped much of the landscape of Westland.  The torrents of rain bring debris eroded from the mountainsides down to the lowlands and created the wide, fertile floodplains upon which the rainforests grow: themselves nourished by the constant wetting rains.  Eventually, every drop of water - from the glacial ice to the run-off of tiny streams -  returns to the Tasman Sea to be recycled into seawater and eventually returned to the clouds to once again fall on the forests and ranges of the West Coast.

The Wet Land

To early Maori, the rainforests and swamps of the West Coast presented an almost impenetrable barrier.  But with patience and skill, Maori learned to harvest what they needed from the wet land: especially Pounamu, the lustrous green stone carried down from the mountains by the tumbling rives of South Westland.  Subsequently, the European settlers found timber in abundance and sawmilling was one of the main industries of then early West Coast economy.  As the rainforests were cleared, the land was brought into production for beef, sheep and dairy farming.  However the swampy, infertile soils could only be farmed once drainage had been established.  Even today, farmers have to balance the bountiful rain with the problems of flooding, erosion and the leaching of nutrients from the soil.

Humus is Everything

In a rainforest, nothing goes to waste.  Leaves and bark, fallen branches, seeds and whole trees fall to the forest floor and slowly decompose into the rich, black humus and soils upon which the rainforest grows and thrives.  The humus holds the rainwater like a giant living sponge, preventing it from running off and eroding the forest floor.  The big rainforest trees, such as kaihikatea and matai, have shallow root systems and depend on the rich humus for their nutrients.  Mosses and ferns carpet the rainforest floor, adding to the sponge-like feel you get when walking through the forest.  The waters of the tiny creeks, which wend their way silently through the forests, are stained brown by the tannins which bleed from the humus as it decomposes, giving them the colour of the black billy tea brewed by the early explorers as they made their way through these dense and beautiful forests.

The Deep Dark Forest

Step a few metres away from your vehicle in a rainforest glade and turn around.  Can you still see your car?  Probably not.  The thick understory of the rainforest forms a green barrier which can quickly shield landmarks from view.  The early explorers found navigating and route-finding extremely difficult in the rainforests of the West Coast and would often spend days, even weeks, completely lost.  Lush tree-ferns, bushy coprosmas with their round leaves and tiny coloured berries, five-finger trees with their hand-shaped leaves and dozens of other low-growing species fill every available space on the forest floor with foliage.  And then…you look up.

The big guys of the rainforest are the trees.  The trunks of the kaihikatea, matai and rimu trees stand ram-rod straight in the swampy ground, swaddled with creepers and dangling vines.  The 19th century writer Joseph Conrad once described visiting the Congo rainforests as being like going back to a time “when vegetation rioted on the Earth and the big trees were kings.”  And when you stand in a forest of towering kaihikatea trees in the silent, dripping rainforests of Westland, you can easily imagine the pre-historic times before people came to these islands and the big trees really did rule the Earth.

The Living Forest

The rainforests of the West Coast are alive with life.  New Zealand has always been a land of birds, and despite the ravages of introduced predators – such as stoats, rats, possums and cats – if you stand quietly in the forest you will hear a symphony of bird-song.  The limpid notes of the bell birds and tui provide the melody, while the trill of grey warblers, the “chit-chit” of riflemen (New Zealand’s smallest bird) and the cork-on-a-bottle peep of the friendly fantail provide the harmonies and percussion.  At night you may hear the mournful cries of the kiwi and the strange call of the ruru, New Zealand’s native owl, which seems to say “more pork”, hence its English name.

A colourful profusion of flowers can be seen in the rainforests and depending on the season, you will encounter rata, with its bright crimson flowers; perfumed white clematis; tiny pale blue coprosmas; and the spectacular yellow of the kowhai.  But the overwhelming dominant colour is green, and in the rainforests of the West Coast, nourished by the constant rainfall and temperate climate, you will see every shade of green you can possible imagine.  Just make sure you bring a raincoat!

For more information about Franz Josef and the West Coast, check out Westwood Lodge.

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