Animal Land Makers.

Timaru Herald, Volume XIC, Issue 13397, 21 September 1907, Page 3 (Supplement)

Animal Land Makers.

ALTERING THE MAPS: In Newport River, and Beaufort iiar-' bour. on the coast of North Carolina, are a-number of small islands. Some'are mere sand banks, others are five to ten acr«j of sound- green - grass and palmetto scrub. It has been noticed for many years past that these islands- are. growing-, as if they were coral reefs, and a geologist, Dr." .Grave, has been-. investigating the cause. He finds that -they are built entirely by oysters. Ages' ago, 'oysters settled on the mud banks. .Young, oysters muist have clean ground to'.fasten; .-upon. Therefore the spat settled on the outer edges of the colonies where the tides and. currents kept the nwid- from settling, and in- this way the ovster reefs grew across the current. In course of time sand covered up the succeeding generations of oysters, and slowly the reefs grew till they: poked their heads* above water and became islands. .So-called coral insects have, of course, done mora to alter the surface of our planet ' than anv other creatures. It is- odd" how little- the average person knows' about coral builders. As a matter of fact, there are scores of different kinds of creatures which build coral reefs. Some are polyps, some madrepores, others seaanemones, but all have one point in common. They every one take lime from the sea water for the purpose of building a bony base or skeleton, and it is this lime which, after the creaturns themselves are dead, remains for fresh generations to grow upon. They have been building for millions of years past, and over 1,800 fossil kinds of "coral buildenr have bsen classified. Some of their works are gigantic. Coral ato!s run to ninety miles long, and as much as ten wide;" while the Great Barrier reef along the Queensland coast is no less than- 1,200 miles long, and in all its immense length has but one passage for ships. It is estimated'tliat the land formed by coral builders furnishes to-day a dwelling place for more than 5,000,000 of the human race, and the prodigious amount of work which-, these never-curing buildens have -accomplished .is-proved by the fact that over two'and a half millions of square miles of sea bottom are paved with coralline ; sand and mud.

Shell fish are- not peculiar to the sea coast." Tlie;.whole of the world's oceans are full of tiny shell fish, and these creatures are slowly-Causing enormous changes in the configuration of our globe. All tlie pleasant, turfy chalk downs of Southern England are composed entirely of the remains of the tiny "shells of creatures which once floated in the warm waves of a' prehistoric sea. At present nearly 50,000,000 square miles of the. beds of the world's- oceans are covered' with Globigerina ooze, a soft, grey mud chiefly composed of f!he remains of minute shells.

One of the oldest of geological mysteries is the discovery of gigantic beds of fossil shell fishes in Colorado. These cover nearly 800 square miles in the Green River District, and in some places the fossil fish lie 150 feet thick. How the creatures got there in such masses is a complete puzzle, especially as the country where they are found is about 8,000 feet" above the present level of the sea.;

Apart from purely marine worms and ants have done and are doing more to alter the face of tie dry land than any other living creatures. Those who have read "Darwin" know that there are on an average 53,000 worms, to the acre, and that these creatures raise ten tons of soil to the surface yearly: At this rate they change the whole top surface for a depth of three inches, fifteen years. If there were no worms the rain, could hardly psnei-tate clay soils, 'arid., so these would not be worn away as they are. Ants do not materially affect the lie of the land in temperate climates, but in • the .tropics they completely change the surface; and termites, tli3 so-called -white ants, do an even vaster work than tjk trufflants. \ All dead timber is reduced to dust, and every morsel of organic matter, whether a dead' rat or a d*ad elephant, is cut up into fragments and carried off. But for the labours of ants all tropical forests would be utterly impassible. The forests of Southern Alaska, where termites do not exist, are, as a matter of fact, completely blocked by fallen timber, which lies whwe it falls until it slowly decays.

Of four-legged anirna's none can compare with the beaver as map-maker. The beaver is the most untiring engineer in existence, and has dams, one of which, examined by Mr Morgan, was found to be 1,530* feet long, have turned vast areas ,of forest into swamp, and have in many cases diverted the courses of rivers.

All through the vast North West, you will find great openings 'in the forest, glades covered deep with peat and bearing only coarse grass. Thess gladesj which are sometimes hundreds of acres in extent, are the siUis' of ancient beaver lakes. Either the dams have burst, and the water run away, or else peaty deposits .have filled up the site of the ancient lake. .

We find fossil skeletons of a beaver, the Castoroides ohioensis, which was about the ■size o'f a black bear. . Such a creature must have been capable of completely altering any landscape, and no forest monarch could have been 'safe from his monstrous incisors.

Some aniamls have the peculiar and very unpleasant property of being able to turn a fertile country into a howling desert. Of these the worst offenders are sheep. A large part of New Mexico has been converted into sandy desert since siheei>farming began in that territory. The soil is naturally light, and while cattle do no harm, sheep in grazing pull up the'tufts of grass by the roots and so destroy it entirely.

Goats act in similar fashion. Early in the sixteenth century St. Helena was covered with den** forest-. In 1513 the Portuguese introduced goats. Thecse multiplied lapidly, and soon destroyed all the

young trees. Thus tha torrential rains got. hold of the soil, and, washing it down the slopes, left the hill sides bare. By 1720 the forest had practically vanished, and the island's beauty was ruined. A third desert-maker is that pretty little marmot known as tha prairie dog. So fast do they multiply that a "town" of prairie dogs near Kushville, in Nebraska, destroyed 3,500 acres of good pasture in thrse years.

Animals also do good work as rroadmakers. The great trials made by the now extinct buffalo in their annual migration:-; across the Western prairies are still plainly visible, wide, hard-beaten depressions. The monstrous brown bear of Alaska, which is nearly as big as an ox arid" weighs up to half a ton. is also a first-clas> road-maker. All along the banks of the streams the miner finds fine, broad trails trodden out. But woe betide the human ihvader if he meet the original engineer when trespassing on his domain!