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What? Desertification in the Catlins?

I can't believe what I saw today - the first stages of desertification in rainy, temperate New Zealand. How is that possible?

When I visited Torrey Pines State Park years ago near San Diego California, I was not surprised to see desertification in action. Wild grazing animals native to the region like deer, Elk, and even mammoth further back had been long ago hunted to the dark reaches of human memory. They formerly were essential components of the central and southern California savanna ecosystem because they kept grasses healthy. Grasses rely on grazing herbivores to survive in places with seasonal or low rainfall.

As Allan Savory has pointed out to the world, grasses cannot shed their leaves like trees and if herbivores do not remove old dead leaves or trample them to bits to let light down to the growing points at soil level, the grass plant eventually dies for lack of light – it smothers itself. Grazing animals and grasses are in mutually beneficial symbiosis. The grass provides food for animals from photosynthesis and the animals fertilize and prune the plants for optimal productivity. Isn’t nature clever?

Accumulating dried dead leaves on top of growing points are lethal to grass plats if left intact in semi-arid parts of the world like Southern California. Because it is usually very dry all summer, the dead leaves don’t rot away as it would where I have farmed in more humid Vermont and New York State where bacteria, fungi, and other decomposing life, helped by moisture would get decay accomplished soon enough for the grass to send up new shoots to photosynthesize and make food for the plant. In California, without wild grazing animals or tame livestock to prune off dead oxidizing material and rejuvenate the grass, the plants die and then their ability to hold soil together with their dense mat of roots is lost and soil erodes away – the first step of desertification. The dead material also becomes tinder for wildfire as you can see in the photo I took at Torrey Pines which had massive amounts of erosion occurring on adjacent slopes.



While I would expect desertification to begin on semi-arid grassland with all grazing removed, I couldn’t believe my eyes last week when I saw this very process occurring here in the humid Catlins region of New Zealand where we get 800 to 1,100 mm if rain per year and enough in the summer to keep grass growing.

Check out these bunch forming grasses snuffing themselves out where sheep and cows have been fenced out to plant native trees and grasses

The South Island giant moa and the Heavy-footed moa once would have ripped this thatch material swiftly away with their bear-clawed feet the size of dinner plates and kept native poa species and even tussock healthy and green. Pictured below are the bones of the Heavy-footed moa at the Otago Musuem.

In their absence, native grasses are dying and loosing their footing, exposing bare soil as you can see here with new areas of oxidizing grass nearby which is bound to expand this area of bare soil.

On these sloping headlands at Long Point, bare topsoil will swiftly wash away in the driving rain or even blow away when exposed to fierce southerly winds making this spot more brittle than sheltered areas nearby (read about the brittleness scale in Allan Savory’s book Holistic Management)

This adjacent bare eroded area which has lost up to 80 cm of soil may have succumbed to the same process of “desertification” Allan Savory explains so well and that I have seen occurring in every country I have been to dry or rainy.

In the foreground, dead oxidizing grass is in the process of expanding this bare and eroded area.

Replacing natural wild grazer behavior with livestock managed to behave like their wild ancestors did, Savory believes will allow people to manage grasslands to keep them healthy and allow nature to re-cloak bare desertified land in seasonally dry areas. I reckon this same tool is essential to keep grasslands or mixed grass/forest healthy even in more humid temperate places - where they once covered the landscape such as most of Europe and North and South America.

Notice on the far side of the fence where sheep still graze, the ground has a solid soil armor cover of growing healthy grass and there is no bare soil whatsoever. Where nothing grazes in the foreground, there are large patches of oxidizing dead grass smothering the grass and subsequently roots will not hold the soil in place in severe weather.

Should the Department of Conservation consider allowing livestock to return at times once the native trees they have planted are big enough to be unharmed to prevent this erosion from getting worse? Surely soil is worth conserving. The complete removal of grazing livestock by DOC in semi-arid areas like Central Otago should be considered carefully with full understanding of how the pristine ecosystem worked. Presently, livestock are now pruning and fertilizing plants which were once kept healthy by megafauna like New Zealand moa and possibly can be managed to better mimic this essential ecosystem service.

Yes, poor grazing management had done untold damage to landscapes around the world. But with better understanding of how grassland ecosystems work, farmers can use livestock to mimic nature and restore long lost productivity to help keep our planet green and water cycles healthy. If you want to learn more about how this is possible take a look at my talk to New Zealand farmers who are interested in doing just that.

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