Scientists generally consider biodiversity as containing three elements.
1. Genetic diversity: This is the genetic variation within a species. How are our three species of kiwi related to each other genetically and how do they differ? .
2. Species diversity: What different types of species are found in the area?.
3. Ecosystem diversity: This is the different environments where things live such as rock pools, tundra, forests as a few examples.
In considering biodiversity scientists also look at the roles these elements play within the ecosystem. Many organisms play crucial roles within there environment, these are keystone species , they may provide food (phytoplankton), recycle nutrients (bacteria), control lower predators (ladybird), pollinate plants (Birds/Insects). Often the relationships between species is subtle. When one species declines, other species that are linked to it may decline or increase in number. .
Why should this concern us? .
Many of our indigenous species are endemic and few have adapted to the introduction of predatory or competing species, the alteration of their habitats through urbanisation, clearing of forest for farmland and alteration of water recourses for hydropower and irrigation. The main pressures on biodiversity are hunting, habitat destruction and pests.
The flora and fauna of New Zealand evolved in the absence of mammalian predators and have no adaptations to combat predation or competition from introduced species such as possums which eat their way through an estimated 10,000 tonnes of our native forests each night and eat eggs from nests of threatened native birds (source-Landcare research brochure). They can also spread bovine tuberculosis to our economically important dairy herds. Takahe compete poorly with deer who have the upperhand in the takahe's remaining habitat. Another example of introduced pests is the varroa mite which attacks adult honey bees and their developing larvae.
