Farm Forestry New Zealand

Patching Earth’s quilt - Planting trees for people, profit and the planet

Henrik Moller, New Zealand Tree Grower May 2013.

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Vegetation of all sorts builds the soil and keeps it together and moist so the fungi, bacteria and earthworms can make nutrients available for plants. Pasture and stock feed and clothe people, and trees provide materials and shelter. By turning a healthy profit, farmers and foresters can maintain a presence on the land and so look after it. We need to plant more trees to help patch up earth’s quilt to keep our production landscapes going. That is why New Zealand tree growers are my heroes.

Plant trees to retain water and nutrients

Unless a farm is irrigated, intensive agriculture usually dries out the land. This is partly because many wetlands, even small seepage areas in gullies, are drained and replaced by pasture. Tile and mole drains are often inserted into heavier soils to maximise pasture production by aerating and warming the soils faster in spring. More generally, removing the trees opens the land to direct sunlight and allows the wind to reach ground level.

Unless farmers use minimum tillage strategies such as direct drilling, a hot dry summer wind will rob the top soil of its water, blow it on to the neighbour’s property or into a stream. In the past, when it poured with rain, tree roots held the soil together, even on the steeper sites. Trees and the forest litter, nature’s mulch, stored a lot of the water and released it more slowly back into the air or into the streams and rivers at a gentler pace, in most cases with little sediment suspended in it.

If the right trees are planted in the right places, an observant farmer will see lots of subtle signs of improvement. A temporary stream will flow more steadily and for more of the year, a paddock will stay greener for longer as a drought sets in and bounce back faster when it breaks, or the stream will run clearer where it leaves their property than where it entered upstream from a neighbour who has not planted trees. We need to get more trees out there on farms, and quickly.

Preparing for climate change

Climate change is under way and is going to get worse – some areas will receive less rain overall, others more. However the biggest threat from climate change is not the gradual shift in average rainfall and temperature, it is that the rain will be more erratic. We can expect and must plan for more frequent and intense downpours or snow dumps, and longer and more severe droughts on the other.

Much of the damage to soil structure, pasture, trees and stock occurs during these short and intense events when ecosystems and farming are tested to their limits. That is when most of the unwelcome sediments and their valuable organic matter and nutrients are flushed into our waterways too. Stressed ecosystems, especially those with sparse vegetation, are particularly vulnerable.

The photograph shows the Waimakariri river mouth and gives some clue of what we flush into the sea up and down New Zealand every day. Some sedimentation is a natural part of our geology and ecology, but the loads are greatly increased by replacement of forests with intensive farming. The result is generally out of sight and therefore out of mind.

If we could suck the water out of the sea for just a minute, many New Zealanders would get a wake-up call. They would see the shelf, slopes and gullies of the sea bottom oozing and clogged with gunk. It is estimated that a layer of mud, up to two metres thick, was flushed across the inner to middle Poverty Bay shelf following the 72 hours of rain dropped by Cyclone Bola in 1988.

Silting smothers reefs and breeding grounds for species like paua, and also cuts the light penetration for the seaweeds to grow and develop a whole inshore marine ecosystem. The big seaweeds, macro-algae, are the ocean’s equivalent of trees. They oxygenate the water, trap energy, provide habitat and generally keep the ecosystem going. Flushing soil and nutrients out to sea is a waste and it clogs our estuaries and harbours. Tree growers and farm foresters have a nationally important task in front of them – to get the right trees in the main places to reduce the sediment and nutrient run-off.

Anyone leafing through recent issues of the Tree Grower will quickly understand that farm forest farmers are long- term risk managers. They are the sort of experts we need to re-create, care for and renew a patchwork quilt of trees, pasture, native grasslands and wetlands throughout our production landscapes.

Climate change offers another, although somewhat indirect, incentive for farm foresters. Your trees mitigate the problem because they capture and store the atmospheric carbon which is causing it. Afforestation and rebuilding organic carbon content of agricultural soils are the two main ways New Zealand can sustain intensive agriculture in the face of climate change pressures. Integrating efficient agriculture with forestry in farmed landscapes is the obvious way forward.

The carbon market has slumped recently, but it is inescapable that it will come back strongly when politicians get us through this global recession. Foresters are stayers, not racers. They have the long-term planning and investment vision that the planet needs to head off climate change. If I had spare funds, I would be investing in forestry now.

Henrik Moller is a researcher at the University of Otago’s Centre for Sustainability. He promotes holistic approaches to land management by combining qualitative and quantitative approaches to bridge ecological, social and economic sciences with local practitioner’s knowledge.