Provision of Natural Habitat for Biodiversity: Quantifying Recent Trends in New Zealand (original) (raw)

2011, Biodiversity Loss in a Changing Planet

Introduction 1.1 Biodiversity and habitat provision in New Zealand The Millennium Ecosystem Assessment (MEA) found that over the past 50 years, natural ecosystems have changed more rapidly and extensively than in any other period of human history (Millennium Ecosystem Assessment, 2005). In the 30 years after 1950, more land was converted to cropland than in the 150 years between 1700 and 1850, and now one quarter of the earth's surface is under cultivation. In the last decades of the twentieth century, approximately 20% of the world's coral reefs have disappeared and an additional 20% show serious degradation. Of the fourteen major biomes in the world, two have lost two thirds of their area to agriculture and four have lost one half of their area to agriculture. The distribution of species has become more homogeneous, primarily as a result of species introduction associated with increased travel and shipping. Over the past few hundred years, the species extinction rate has increased by a thousand times, with some 10-30% of mammal, bird, and amphibian species threatened with extinction. Genetic diversity has declined globally, particularly among cultivated species. A framework of ecosystem services was developed to examine how these changes influence human well-being, including supporting, regulating, provisioning, and cultural services (Millennium Ecosystem Assessment, 2003). While overall there has been a net gain in human well-being and economic development, it has come at the cost of degradation to many ecosystem services and consequent diminished ecosystem benefits for future generations. Many ecosystem services are degrading because they are simply not considered in natural resource management decisions. Biodiversity plays a major role in human wellbeing and the provision of ecosystem services (Diaz et al., 2006). For example, natural ecosystems provide humans with clean air and water, play a major role in the decomposition of wastes and recycling of nutrients, maintain soil quality, aid pollination, regulate local climate and reduce flooding. New Zealand has been identified as a biodiversity hotspot (Conservation International, 2010). Located in the Pacific Ocean, south east of Australia, New Zealand covers 270 thousand square kilometres on three main islands (North, South and Stewart Island). It has a wide variety of landscapes, with rugged mountains, rolling hills, and wide alluvial plains. Over 75 percent of New Zealand is above 200 meters in altitude, reaching a maximum of www.intechopen.com Biodiversity Loss in a Changing Planet 202 3,700 meters on Mount Cook. Climate is highly variable and has played a key role in biodiversity distribution (Leathwick et al., 2003). As New Zealand has been an isolated land for more than 80 million years, the level of endemism is very high, with more than 90% of insects, 85% of vascular plants, and a quarter of birds found only in New Zealand (Ministry for the Environment, 2007). One of the most notable characteristics of New Zealand's biodiversity is the absence of terrestrial mammals, apart from two bat species, and the dominance of slow-growing evergreen forest. New Zealand's indigenous biodiversity is not only unique within a global context-it is also of major cultural importance to the indigenous Maori people. Maori have traditionally relied on, and used, a range of ecosystem services including native flora and fauna for food, weaving, housing, and medicines. The isolation of New Zealand has preserved its unique biodiversity, but also rendered the biodiversity vulnerable to later invasion. When Maori migrated from the Pacific Islands, circa 700 years ago, predation upon birds began and much lowland indigenous forest was cleared, especially in the South Island. Rats and dogs were also introduced. The birds, having evolved in an environment free of predators, were susceptible to disturbance and many began to decline to the edge of extinction. When Europeans arrived in the early 19th century, they extensively modified the landscape and natural habitats. Large tracts of land were cleared and converted into productive land for pastoral agriculture, cropping, horticulture, roads, and settlements. Only the steepest mountain land and hill country was left in indigenous forest and shrubland. Swamps were drained and tussock grasslands were burned. Not only was the natural habitat significantly altered, but a large range of exotic species were introduced, including deer, possums, stoats, ferrets, and weasels, causing a rapid decline in native birds and degrading native forest. Other introduced plants and animals have had significant effects in the tussock grasslands and alpine shrublands, most notably rabbits, deer, and pigs, and the spread of wilding pines, gorse, broom, and hieracium. Despite significant efforts to control weeds and pests and halt the loss of natural habitat, around 3,000 species are now considered threatened, including about 300 animals, and 900 vascular plants (Hitchmough et al., 2005). The Economics of Ecosystems and Biodiversity study (TEEB) suggested that it is difficult to manage what is not measured (TEEB, 2010). To prevent further biodiversity loss, decisionmakers need accurate information to assess and monitor biodiversity. However, biodiversity assessment is not a trivial task. As defined by the Convention on Biological Diversity (CBD), biodiversity encompasses "the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems" (CBD, 1992). Conceptually, biodiversity is a nested hierarchy comprising genes, species, populations, and ecosystems. In order to assess status and trend, these multiple levels need to be assessed simultaneously. Noss (1990) suggested a conceptual framework with indicators providing measurable surrogates for the different levels of organisation. Loss of extent is one of the many indicators in this framework, and it has been widely used internationally in reporting to the CBD (Lee et al., 2005). It is relatively easy to report, and has been recognised as one of the main drivers for biodiversity loss (Department of Conservation [DOC] and Ministry for the Environment [MFE], 2000). 1.2 Previous assessments in natural habitat Several national surveys of vegetation cover have been completed. The New Zealand Land Resource Inventory was derived by stereo photo-interpretation of aerial photographs