Environment of New Zealand

[1] The main islands of New Zealand span two biomes, temperate and subtropical, complicated by large mountainous areas above the tree line.

Historically having an isolated and endemic ecosystem far into modernity, the arrival of Polynesians about 1300 AD[3] and then later European settlers began to have significant impacts on this system, with the intentional and unintentional introduction of new species and plants which often overwhelmed their natural competitors, leading to a significant loss of native ecology and biodiversity, especially in areas such as bird life.

Today, most parts of New Zealand are heavily modified by the effects of logging, agriculture and general human settlement, though large areas have also been placed under protection, combined in many cases with efforts to protect or regenerate native ecosystems (aided by the fact that especially the South Island of New Zealand has a very low population density).

These include local events with short return times like landslides, floods, el nino and fires (rare before the arrival of humans).

[4] Long term events like massive eruptions and glacial maxima have also affected the current distribution of species in New Zealand.

[5] New Zealand's soils are affected by bedrock, climate, vegetation and the time it has had to develop, In the central North Island the felsic volcanic rocks is deficient in elements (like cobalt) needed by plants.

The main geographic factors that influence New Zealand's climate are the temperate latitude, with prevailing westerly winds; the oceanic environment; and the mountains, especially the Southern Alps.

Conditions vary sharply across regions from extremely wet on the West Coast of the South Island to almost semi-arid in Central Otago and the Mackenzie Basin of inland Canterbury and subtropical in Northland.

However, the combination of external factors such as climate change and invasive species, as well as increasing agricultural and other human land uses have led to widespread damage.

Native deciduous plants are extremely rare, with only 11 species losing all their leaves in winter, none of which are common canopy forming trees.

Beech forests are divided into four varieties based on the dominant tree species and their geographic distribution is largely related to elevation.

The effect of the whole canopy flowering at the same time introduces a lot of food into forest at once and leads to a population spike in those species that can quickly respond (typically mice).

[20] New Zealand has extensive natural tussock grasslands in locations where elevation and climate has limited forest growth.

There are also smaller areas of tussock grassland on flood plains due to the constantly shifting substrate and greater likelihood of frost.

[18] Tussock grasslands also help transfer water from the upper to lower catchment due to comparatively low transpiration.

[23] As the Southern Alps were uplifted relatively recently far from other mountain chains the New Zealand biota has quickly adapted to the new environment.

There are also ecosystems where the physical environment is largely controlled by animal activity, such as areas of significant guano deposition.

[32] Farmland and urban environments are marked by the high number of introduced species, that have not evolved to interact with each other in the same ecosystem.

These landscapes can affect the local climate, such as the 2.5 °C temperature rise in Christchurch from the urban heat island effect[33] or the decreased transpiration from farmland.

In the past 800 years of human occupation New Zealand has lost about 75% of its forests due to deliberately lit fires and land clearance.

[citation needed] in 2011 the Parliamentary Commissioner for the Environment claimed the use of 1080, a pesticide using sodium fluoroacetate, was "effective and safe".

[42][43] However its use remains contentious, with debate between conservationists and livestock farmers on one side and hunters and animal rights activists on the other.

New Zealand also has nine wilderness areas where air access is limited,[52] numerous "mainland islands"[53] and marine reserves.