Exotic Forestry – An Environmentally Disastrous Monoculture?

by Ben Hope

Recently a Radio NZ investigation revealed the four largest private landowners in New Zealand are all foreign-owned forestry companies.
In the 2017 election campaign, Labour, Green and NZ First parties  all promised a clampdown on farmland going to offshore buyers. But the Labour-led government has actively encouraged further foreign purchases of land fr forestry through a stream-lined “special forestry test.” 
Since the government was formed, the Overseas Investment Office (OIO) has approved more than $2.3 billion of forestry-related land sales – about 31,000 hectares of it previously in New Zealand hands. Of that, about half has been sold via a special forestry test introduced by the government last October.
Advertisements by forestry bodies such as New Zealand Wood extoll the environmental benefits of “plantation forestry” claiming  they “stabilise hillsides, protect soil health, purify water, regulate its flow and help prevent flooding.”
How do the claims stack up?  Well the term New Zealand Wood is a misnomer as New Zealand pine forests are largely foreign owned as Radio NZ discovered.
Well pine forests do stabilise hillsides at least for 25 years until clear felling at harvest time exposes whole catchments to any rains and subsequent runoff of silt and debris into streams, rivers and ultimately estuarine areas. Studies of the Marlborough Sounds revealed alarming levels of sedimentation with adverse effects on inshore ecosystems and fish numbers.
Doubtful Claims
Claims of enhancement of soil health, water purity and regulation of flow are all dubious.
In the UK information from studies in southwest Scotland point to a strong relationship between salmon fishery catch figures falling alarmingly since 1960 about the time pine forests were extensively planted. Sources point to one detrimental aspect being acidification.  The pH level (degree of acidity) is important to both bottom fauna and subsequently trout. If the pH drops below 5.5 (increased acidity) then long term damage to the fishery, both native and trout, occurs. 
The UK’s “Trout and Salmon” magazine said “conifers are highly efficient at taking and filtering acidity so that it flows through the soil and water beneath them. Thus acidic loading increases as the trees grow.”
Thirsty Pines
Pine forests do regulate water flow but more reducing normal natural water  runoff. A pine tree is said to use 85 litres of water a day whereas a native tree, dependent on species, uses considerably less. Water from a pine forest with a “bare” pine needle forest floor has quicker runoff compared to a typical native forest area with shade-loving undergrowth. In a few words, native forest has a higher water retention factor leading to un-reduced, more consistent stream flows. 
Anecdotal evidence points to streams much reduced in flow once monocultures of pines have been established.  For example, long-time residents where exotic pines have ben planted have observed the same diminished flow after extensive monocultures of pine forests were established.
 The adverse effects begin from day one when at planting time, native bush is usually cleared, often by burning. In one case in Marlborough, a foreign-owned Malaysian corporate with extensive forest ownership throughout NZ, have burned former hill or high country stations of native bush and bracken, roaded it in very steep country with slipping into gullies and planted pines for carbon trading. The original merino sheep stations were “holistically” farmed with stable ecosystems.
Clear Felling
 Twenty or thirty years later at harvesting time, the practice of clear felling pines exposes often steep hill country to heavy rains and runoff of silt and debris. In some European countries, apparently felling is in done in two cuts perhaps 12 months apart, along contours thus reducing runoff. Information suggests the US have enlightened forest felling regimes instead of total clear felling of hillsides. 
One comment from a New Zealander who regularly visits the US – “I noticed when flying to Alaska each year is logging over Washington State and Oregon forests is clearly done on a patchwork quilt basis – not entire hillsides and mountains all planted at the same time and then logged at the same time.”
Clearly claims by the vested interest body Wood NZ are open to challenge.
Perhaps what is needed is:-
(a) Better harvesting regimes as practised in Europe should be implemented
(b) Local council zoning of land should avoid extensive commercial forestry monocultures.
(c) Buffer zones (50 metres) should be mandatory along all rivers and streams.

© Clear felling of a commercial pine forest on a steep hillside

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