Biodiversity

New Zealand’s rural land supports a wide range of productive uses, including horticulture. Managing this productive land sustainably is crucial for this country’s economic and environmental future. This productive land environment also plays a crucial role in New Zealand’s culture and society.

Prior to clearance for productive purposes, rural land supported a wide range of native species. Today, most native flora and fauna have disappeared and the majority of species found on productive land are introduced. Most native species have been marginalised to small pockets of native forest and wetland areas on private land.

Nearly two thirds of New Zealand’s land is held in private ownership. Of this, only around 150,000 hectares is protected through legal mechanisms. This can be compared to the around eight million hectares of publicly owned land which is legally protected. Much of New Zealand’s rare and threatened native biodiversity is found on private land; some species are now only found on private land. ⁴¹¹²

Many of the habitat types and species that are under-represented in the public estate depend upon the remaining fragments of habitats on private land for their survival. ⁴¹¹³  This is most notable in the lowlands where the impact of agricultural intensification is concentrated. This is the area of most concern in regard to biodiversity loss. ⁴¹¹⁴

Value of biodiversity to productive land

New Zealand’s land-based primary production – including horticulture – is reliant on the protection and management of biological systems. The variety of species found on productive land (both native and introduced) have many direct and indirect commercial production benefits, ⁴¹¹⁵  including:

• Production of food, medicine, clothing and timber
• Pollination of crops
• Biological control of pests, weeds and diseases
• Improvement of soil formation and its microbial activity
• Increased nutrient retention
• Improved air and water quality
• Erosion prevention
• Capture of carbon dioxide by plants and carbon by soil

In addition, retaining biodiversity on productive land may assist in marketing goods to the green consumer market and supporting on-farm tourist activities. Therefore, when biodiversity is lost from farmland, it is not just the loss of species of conservation value that is occurring but also the loss of organisms that can provide substantial commercial benefits. This type of biodiversity is often called ‘functional agricultural biodiversity’ and its functions, increasingly referred to as ‘ecosystem services’, can be wide-ranging and of much value to landowners. ⁴¹¹⁶  Much of the production in agriculture depends on these ecosystem functions and processes.

Threats

The most pressing issues facing the protection and restoration of native biodiversity on productive land are accelerating land use change, invasive pests and weeds and land management practices such as drainage. All of these are driving farmland towards a low diversity environment. While rural land owners desire to achieve financial returns from their land, it is important that biodiversity on productive land is protected, because of the essential ecosystem services it provides.

Expansion and intensification of agriculture

The expansion and intensification of agriculture is destroying habitats for indigenous species. ⁴¹¹⁷  Expansion of agriculture into previously forested areas causes a reduction in habitat. Habitat loss remains a primary cause of indigenous biodiversity decline. ⁴⁶⁵⁷ However little horticultural development occurs on previously forested land. Most often the land sought for horticultural development was formerly pastoral or dairy production land. Often the lower value production land can be treated with more sensitivity to increase biodiversity. 

In 2007 the Minister of Conservation and the Minister for the Environment issued a statement which outlined the national priorities for protecting rare and threatened native biodiversity on private land, in an effort to focus conservation efforts on private land where the need is greatest. Whilst some landowners have taken steps to provide formal protection to these habitats, much remains unprotected and at risk.

Invasive species

Although there has been significant progress in the battle against introduced weeds and animals on productive land, the increasing rise in the number of invasive alien species is still recognised as one of the major threats to biodiversity. ⁴¹¹⁸  A sizeable proportion of the projects funded by the Biodiversity Condition Fund (a Government fund for biodiversity protection programmes on private land) are now targeted towards controlling weeds on productive land. There are three main ways that plant, animal and insect pests can be controlled on productive land and these are often combined:

• Physical control – which involves either manual or mechanical removal
• Biological control – which uses a biological control agent, or another living organism, to manage pests
• Chemical control – which requires the use of herbicides, insecticides and vertebrate toxic agents(discussed further below)

Landowners themselves are spending millions of dollars each year actively managing productive land areas through weed and pest control. ⁴¹¹⁹  The 2005 review of the Biodiversity Strategy noted concerns that there was no apparent increase in research efforts to identify new tools and methods to control pests or to address new invasive species.

Poor land management practices, including increasing use of agrichemical inputs

Today, many farms are reliant upon the inputs of fertilisers, pesticides and herbicides to run a successful operation. The effects of agricultural chemical use can be long lasting. For example, the agrichemical DDT was used by New Zealand farmers during the 1950s and 1960s, primarily to kill grass grub and porina caterpillars. Although its use on farmland was prohibited in 1970, high levels of DDT accumulated in the country’s soils during the years of heavy application. Many New Zealand soils still contain high levels of DDT.

The key issues arising from the use of toxic chemicals on productive land include:

• Impacts on the hydrological cycle as toxins run off into the waterways and end up accumulating in the groundwater and marine environment;
• Pollution of the soil with the accumulation of heavy metals; and
• Eradication of insects and beneficial pollinating species which are integral to productive land systems. 

In the 1980s the horticulture sector undertook a substantive review of the management of agrichemicals leading to the creation of a New Zealand Standard: NZS8409: Safe Management of Agrichemicals. This was accompanied by the development of a national course known as GROWSAFE. As part of the program; a model was developed to determine safe limits for agrichemical discharge in order to protect water quality known as the GROWSAFE Agrichemical Calculator. 

Last updated at 6:25PM on February 1, 2018