Almost 60% of New Zealand farmland is susceptible to erosion.
Soil erosion results in loss of land and crops, reduction in yield, fertiliser depletion, damage to structures such as roads, fences, bridges and houses, silting up of rivers and streams, wearing down of river banks, waterlogged soils and devastating marine life when silt flows into the sea.
Erosion is one of the biggest limitations to New Zealand’s pastoral production. Fresh erosion immediately reduces pasture growth by 40-100%. Even after regressing, it causes ongoing reductions in crop and pasture yield of up to 80%.
Loss of soil through erosion occurs from deforestation, overgrazing, rainfall and flooding, wind, gravity causing soil creeps, slips or slumps, housing developments and road construction.
Soil is a non-renewable resource – once lost, it is gone forever.
Planting trees helps prevent farmland soil erosion particularly on erosion prone coastal and inland hillsides and gullies. The leaves of trees protect the soil from raindrop impact and runoff. Transpiration dewaters the soil so it is less heavy and less prone to move. Roots weave through the topsoil into the subsoil below, stabilizing slopes by binding the soil mass together and to the underlying rock.
Restoration of eroding land requires fencing to prevent grazing with planting of native shrubs such as manuka and flax which provide protection to enable larger tree species to regenerate often as a result of seed dispersal by birds.
So effective are trees that the risk of erosion is minimized in as little as 5 -7 years after planting.
And whats more trees create new habitats for our native flora and fauna, improve landscapes, remove damaging CO2 from the air and provide shade for stock along planted margins.
This is one of the core areas of focus for the Trees for Survival planting programme.