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Sunday, October 24, 2010

Terraforming New Zealand - Improving our water resources

Terraforming: To transform the landscape on another planet to resemble the landscape on earth. (wika dictionary)

And that is just about what has happened here in New Zealand. If there ever was a land that looked like another planet, it was pre-human New Zealand and we have terraformed most of it to resemble the northern hemisphere.

Before I start talking about continuing the terraforming, let me make one thing clear. I think that the efforts of Kiwis to turn back the clock to recreate, on islands, the pre-European or even pre-human flora and fauna is wonderful, amazing and very worthwhile. What a great shame we can't bring back the Moa the Hast Eagle and the sea birds.  And I don't confine the definition of islands to pieces of land surrounded by water. In Wellington, for instance, there are the NgaManu and Staglands nature reserves, both of which preserve and encourage native flora and fauna. They are land islands surrounded by pest proof fences in a sea of city and agriculture.

There are also some unlikely types of islands. There are fenced road verges.   In England, they have been found not only to be refuges of plants and animals that are disappearing from farm lands but are corridors for migration. There are military reserves all over the world. Tanks and armoured personnel carriers churn up the soil and practice shooting in these areas so you wouldn't usually think of them as nature reserves. However, people are not allowed in for fear of unexploded ordinance and people are much more destructive than tanks. All manner of species flourish in military reserves. I should imagine that road verges and military ranges in New Zealand also have these benefits.

Potentially, you also have places like wind farms. Put a pest proof fence around a wind farm and let a university come in and eliminate introduced species and bring in natives and you can have islands of native flora and fauna all over New Zealand. This is possible because with a "going concern" (the wind farm) on site with very little impact on the environment, you have enough money to maintain the essential fence. Last but not least, there are home gardens. Plant native trees or bushes and you have many little islands in an urban environment. They provide shelter, leaves for browsing and pollen and nectar for native and also for introduced birds and animals.

All these are great and very worthwhile endeavors but the fact remains that most of the two main islands of New Zealand have been terraformed. If we wanted to turn back the clock we would have to grub up virtually all our forage crops, eliminate cattle sheep and deer, poison our domestic bee, get rid of the earthworms, cut down all our fruit trees and most of our lumber trees and stop growing all of our vegetables. For vegetables we would be left with fern heads and cabbage trees. So lets continue to terraform New Zealand but lets do it slowly, carefully, and with all the precautions we can manage. We have the flora and fauna of all the world to choose from#.

# Have a look at p34 in New Scientist, Jan15,2011 for a take on exotics.

We have to be cautious. We have been stung by the introduction of the rabbit, stoat, weasel, cat, possum gorse and broom. Some would decry the introduction of the many species of deer, the Tahr and the Chamois and the introduction of radiata pine and Douglas fir. We do have a tendency, though, to only see the empty half of the glass.

The rabbit is a huge opportunity for someone who can trap them in large numbers and sell canned curried rabbit to India and canned sweet and sour rabbit to China. Gorse and broom are fantastic nursery species for the planting of forest trees and both fix nitrogen. Deer, Tar and Chamois provide New Zealand with the best hunting in the world. Possum are a source of about the best fur in the world and, mixed with Marino wool  makes the most incredibly tactile sweaters you simply can't keep your hands off of. Our introduced trees provide much of the material for the construction of our houses and support an export industry. For all of that, great caution in introducing new species into New Zealand is of the greatest importance.

And let's say for the sake of the argument that we wanted to bring in a large hunting eagle to nobble up the rabbits.  The black eagle of South Africa would be a likely candidate.  His main quarry is the Dasie.  We would have great trepidations that they would also take lambs.  What to do.  Well, we could bring in ten or so but all males or all females or we could bring in mixed pairs but neuter them.  Give the males a vasectomy so that they would behave completely normally but couldn't have young.

My own favorite candidate for the next introduction is the Canadian beaver. One unique characteristic of this animal is that you know exactly where every beaver is. They build dams and lodges and cut down trees; mainly willows.  If it became necessary for some unforeseen reason to eliminate them, it is relatively easy to do so.  Moreover beavers are self limiting.  When introduced into a new area they overshoot slightly and then fall back to the carrying capacity of the stream.  However, these aren't  reasons to introduce an animal. It only counters two reasons not to introduce them. You can't say with beavers "Oh but if it turns out badly, we will never be able to get rid of them". You also can't say what if the population explodes.  It doesn't happen with beavers. So what are the reasons 'to' introduce them. The reasons are many and varied.

Water Management
Here in Canterbury where I live, we are on a huge alluvial plane which has been created by the out-wash from our high mountains (alps) to the West.   Rivers drop their bed load as they leave the mountains and drop their silt and clay wherever the stream is slow enough. Historically, beds of rivers have filled up with this material, jumped their banks and start to deposit material in a new location. Our rivers act like giant grouting machines spreading material back and forth across the plains. In the 'modern' era we have stopped this process by building levies on either side of the rivers and by allowing companies to extract gravel (shingle) from the river beds.   Underlying much of Canterbury are alternate layers of shingle  and clay.  When we have high rainfall events in our mountains, within two or three days the river rises, the water rushes out to sea and the river falls again. Canterbury itself, while hardly a desert, is on the dry side of the island. This makes it ideal for agriculture as long as water is available. It has been proposed to build great numbers of small concrete dams in the feeder streams all through the headwaters of our rivers. This is to retain water during periods of high availability and release it when water is scarce. Small dams also hold the water longer on the land and increase aquafer recharge. Why not let the beavers do it for free.

Not only will they build the dams but will maintain them forever. No maintenance needed. No expense. And while concrete dams stop the free movement of various plants and animals along the streams, beaver dams do not.  Better still, our rivers have been primed for the introduction of beavers.  Many of them are full of Willows and Willow bark is a favorite food  of the beaver and the remaining branches, their favorite construction material.

Extending the Life of Man Made Dams
As soon as a hydro dam is built it starts to silt up. Bed load forms a delta wherever a stream flows into the dam and finer material settles all over the bottom. Beaver dams catch all this material before it arrives in a hydro-electric or irrigation dam and extends its life. For hydro-electric dams there is another effect.

Increasing the Electricity Generated from a Hydro Dam
One of the largest reducers  of the total energy which can be produced from a hydro dam is uneven water flow. If heavy rainfall occurs in the dam's catchment, water has to be let out over the spillway rather than going through the generators. This water is wasted. With beavers in a catchment, water is retained during high flows and released during low flows#. The flow of the water into the hydro dam is evened out, increasing the amount of power which can be generated from the same total amount of water flowing through the hydro lake.

# Read Three Against the Wilderness by Eric Collier.  Especially Chapter 27.  It goes beyond belief the extent to which beaver dams can moderate flood events. Available in the Amberley and the Christchurch libraries.
Creating Wetlands

The value of wetlands is too well known to need rehashing. Beaver dams create wetlands as the ponds fill up with silt and organic material. Water plants grow in the pond, die and sink to the bottom and  shore plants encroach from the sides until the pond is transformed into a wetland. Trees eventually colonize the wetland and another colony of beavers establishes itself and the cycle repeats itself. Over time, the valley bottom becomes higher and higher with a ever deepening water holding sponge. The water storage and release function of the beavers handiwork increases over time, further evening out water flow. Wetlands themselves catch silt and bottom load almost as well as the original beaver pond.

Clearing the Water
There are distinct advantages to clear water. Many fish, including trout and salmon prefer clear water, water plants can grow attached to the bottom when sunlight can penetrate and water treatment for human use is less expensive when there is no suspended sediment. Beaver ponds are very good at trapping bed load and suspended sediment.

Removing Nutrients
When too great a quantity of agricultural runoff seeps into a stream, it can become eutrophic* and inimical to normal flora and fauna. Beaver ponds create a detritus cycle which captures nutrients in a form which is excellent food for a wide range of animals while at the same time keeping the water clear. The detritus cycle depends on all the bits of cellulose (wood chips, twigs, leaves) that collect in beaver dams. Beaver dams also increase the surface area of a stream and hence the amount of sun it collects and therefore the amount of photosynthesis from phytoplankton and rooted plants. Photosynthesis also removes nutrients from the water.

*when nutrient levels are so high that toxic blooms of algae occur, die and poison the water.

Ecological Diversification
If you have a forest with a stream running through it, you have two sorts of environment available for plants and animals - namely the stream and the forest.  Add a beaver pond and you have, of course the pond. You also have an area around the dam which is opened up to sunshine which encourages the growth of herbs, grasses and shrubs.   The cleared area can be as much as a hundred meters from the shore although usually much less.    You create two new environments for plants and animals.

Fish Nurturing
Salmon hatch in gravel beds in streams and many salmon species search out quiet areas to grow before they return to the sea. If they have to fight currents all the time, all the energy from their food goes into swimming instead of growing. Beaver ponds are the ideal nurseries for the Salmon family. Moreover, adult salmon, after spawning, die and are held in beaver dams. The beaver dams catch this huge pulse of nutrients which comes up from the sea and stores it in the surrounding ecology. the food, thus created,  is available to the juvenile salmon when they hatch. Beaver dams greatly enhance salmon runs. They also provide quiet pools for trout.  If you have seen National Geographic films of salmon leaping high water falls with a single bound, you will understand that a beaver dam is no barrier to a migrating salmon intent on his once in a life time act of procreation.

If there was ever an animal that would benefit New Zealand it is the beaver.

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