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Wednesday, September 12, 2007

Fertilizing New Zealand - the natural way

Prior to the invasion of the first humans, New Zealand apparently used to receive a constant application of fertilizer. This fertilizer was better in quality and larger in quantity, than what all our farmers now apply to our pastures. It would be possible to get the system operational again but it would take some work.

Before humans arrived, New Zealand had a fauna dominated by birds. The only mammals in New Zealand were Bats. We are all familiar with the stories of the giant flightless Moas. However another set of less publicised birds was arguably more influential on the environment. These were the sea birds. The various species, including our favorite 'mutton bird' fed at sea, and nested on land. Some of them, like the Mutton Bird dug out burrows for a nest where they raised their chicks. Without ground predators the sea birds could nest anywhere between the coast and as far as they could fly with their load of stomach-stored-fish to feed their young. In south Island, the remains of nests have been found as far as the foot hills of the Southern Alps. A remnant colony of nesting sea birds still exists high on the mountains of Kaikura. So what destroyed this system.

The obvious candidate is man who, when he arrived, found a rich, easily captured source of food in the nests of the burrowing sea birds. However, an animal he brought with him was probably an even bigger destroyer of this ecology. When Polynesians traveled in their ocean-going canoes, they often brought along the Pacific Rat. Rats are very adaptable and provided a good source of human food once they become established on an new island. Fish and oysters are great food but every once in a while one wants some real meat. Traces of the Polynesian rat have been found in Moa swamps from long before it was believed that the first Polynesians reached New Zealand. It is possible that a canoe of men-only arrived much earlier than the accepted first-arrival date, or that some natural disaster such as the explosion of Lake Tapo wiped out early settlements. Whatever the case, the rat became established and preyed on the young of the nesting sea birds. Unused to predators, the sea birds never had a chance. If the Polynesian rat wasn't enough, as soon as Cook arrived, the European rat, an even more destructive beast, was introduced and quickly spread.

Before their demise, sea birds deposited large quantities of Guano on the land. Guano is not only rich in the major essential elements but also in all the trace elements needed by plants. Any home farmer knows that if he manages to cage a bag of guano, he puts it under lock and key and doles it out with a teaspoon to his favorite plants. Its effects on plants are legendary.

There are a few systems in nature that reverse the constant flow of nutrients from the land down to the sea, The salmon of North America are one and the migration of eels another. However, the system that existed in New Zealand before the invasion of humans dwarfed these nutrient flows by a several of orders of magnitude. It has been estimated that the quantity of nutrients spread on the land by the sea birds exceeded the amount of fertilizer now applied by all our farmers and it was of a much higher quality.

As an aside, where do our fertilizers come from. Much of the phosphate we have used in the past came from Pacific Islands, notably in Kiribati, destroying the island in the process and along with it the life of the people that lived there. (A Pattern of Islands by Arthur Grimble). There is now talk about scraping off the little bit that remains. The phosphate deposits on the islands were probably the guano deposits from ages of sea birds. Over time guano looses its nitrogenous content leaving behind mainly phosphate. We have mined large parts of these islands down to bed rock, leaving them virtually uninhabitable.

Our nitrogen we obtain mainly by fixing atmospheric nitrogen into compounds (Haber process) and putting it on our fields. There are some ecologists who believe that the resulting warping of the nitrogen cycle - favouring nitrification over denitrification - may pose a greater threat to our world in the long run than our release of geologically sequestered Carbon.

So how could we get the sea birds rather than top dressing planes to fertilize New Zealand again. How could we utilize nutrients from the sea instead of destroying peoples homes and unbalancing the nitrogen cycle.

Fortunately, we don't have to reinvent the wheel. The bones of the system already exist in Namibia.  South western Africa is one of the typical upwelling areas of the world with a desert on land and an incredibly rich marine life offshore. Sea birds abound in this rich area and any little island that Africa's predators can't reach is populated by masses of squabbling birds, all after nesting sites. Because of the lack of rain, the guano builds up and this renewable resource has been collected for decades for fertilizer. However, the African guano companies realized that they could increase their output.

With no lack of fish in the sea, the main limit to the sea bird population is the lack of nesting sites. The guano companies solved the problem by driving pilings into the bottom of some of their shallow bays and building platforms on top of them. This isn't much help to the burrowing sea birds but for the shags, cormorants, gulls and so forth, it provides much needed additional housing. On some of the platforms, a little bob-cat type front-end-loader is left permanently and every year or two they simply scrape off the guano and load it into a barge tied up along side. The question is, how could we best adapt this system to New Zealand.

The first thing to do is to see if it will actually work here. Will a platform set up in a shallow bay actually become populated with nesting sea birds. An ideal site would be near the Marine Laboratory in Portobello where it is out of the reach of storm waves and could be monitored by the laboratory staff. This location has the added advantage of being close to the Circumpolar Subtropical Convergence, an area rich in marine life. Of course the guano might not remain on the platform due to our relatively high rainfall but that is OK. Our initial aim is to see if an added "housing facility" would encourage the nesting of sea birds. Work could even be done to see if burrowing sea birds could somehow be induced to nest on the platform, possibly by providing them with artificial burrows. Then in addition to guano, we might develop a source of mutton birds.

If successful, the next step would be to set up a similar platform somewhere nearby on land. Here the pilings would have to exclude climbing predators such as possums, stoats, cats and rats. It might be sufficient to use the possum guards that we use on many of our wooden power poles or one might need to use steel or cement pilings. This next stage would prove whether or not sea birds would nest on such a platform situated over land. It would also test predator exclusion and would provide more experience with the system.

The third stage would be to put platforms further and further inland and ask a range of questions.

* How is the dung distributed. ( Do the adult birds deposit Guano only when at rest on the platforms or do they deposit dung as they fly.)
* How much Guano is deposited per nest and per area of platform.
* Is guano distribution determined by the distance from the platform to the sea.
* What is the guano composition in relation to plant needs.
* Is the area around the platform so over-supplied with nutrients that it becomes sterile.
* Can the guano be profitably harvested or is it all washed off the platform by the rain. Does this vary at different geographical locations around New Zealand.
* If guano can be harvested what area of platform would be needed to make a farm of a given area fertilizer-independent.
* Can the platforms be modified for mutton bird nesting without interfering with the fertilizer collecting function.
* How large a system would be needed to start up a viable mutton bird business.
* Are there ways of encouraging one species of bird over another.
* How are the nutrients from the platform spread naturally over an area (plants fertilized by the Guano near the platforms, eaten by grazers who spread their dung further afield)
* Are there low cost ways of spreading the dung to lower areas on the farm (via gravity fed water from a pond into which the guano rain-wash is flowing for instance)
* Is there any damage to lambs at lambing time from any of the occupants of the platforms
* Is there any benefit to sheep or cattle fed on Guano-fertilized-grass. (fecundity, birth success, longevity, freedom from disease) when compared with livestock living on grass which is conventionally fertilized.
* Will Guano compensate for the soon-to-be lack of clover (veroa is on the way down South Island)
* Can Selenium prills be dispensed with when Guano is used.
* Can B12 injections be dispensed with when Guano is used
* Is there any difference in the de-worming necessary when sheep or cattle feed on Guano-fertilized grass.

Sustainability seems to be the buzz word in Ecology today and with good reason. We are a plague on the earth and our sheer numbers and gargantuan amount of waste are trashing the ecosystem we depend on. Any steps we can take to be more in harmony with natural cycles will help to reduce our foot print.

At Present we fix atmospheric nitrogen and flush much of it down our rivers, causing eutrophication in lakes and even in large areas of the sea where the rivers debouch. A system which reduces the artificial fixing of nitrogen and simply picks nitrogen up from the sea and brings it back to the land has to be an improvement. A fertilizer which obviates the need to destroy populated islands has to be an improvement.   If a fertilizer which has a much better mineral balance can be obtained at the same time and if it can reduce the fertilizer costs to the farmer, better still.

2 comments:

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Hugh Williams said...

Can someone translate the above comment for me. My portugese is sadly lacking