Biodiversity explained
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Biodiversity is the variety of living organisms in an area and is essential for an ecosystem to sustain life. Those included in the biodiversity of an area can include fungi, invertebrates, birds, mammals and plants. Each provides different resources to other organisms and works in symbiosis to ensure the survival of all life within the ecosystem.
82% of plants and 70% of birds are only found in New Zealand. Before the arrival of humans, Cromwell was dominated by tussock land, numerous kanuka-manuka scrubs and small forests of beech trees and totara. A wide variety of birds (e.g Kiwi, Tui and Moa) were found in the area as well as many unique reptiles (e.g. Otago skink) and invertebrates (e.g. Cromwell chafer beetle). View Exploring Biodiversity video, by DOC |
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Loss of biodiversity
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The arrival of humans to New Zealand over 750 years ago has caused many NZ species to become extinct or critically threatened. Clearing of forests and grasslands for hunting and farming destroyed ecosystems and led to the extinction of many plant, insect and bird species. Biodiverse-rich forests and grasslands that once covered much of Central Otago are now small subsets that are continuing to shrink with fires and pastoral incursion. Those species who rely on them for shelter and food will continue to disappear in unison.
Pest plants grow faster than native plants causing local extinction through shading, increasing acidity of the soil and drying of wetlands. Russell Lupin (Lupinus polyphyllus) are quick growing and can destroy local ecosystems by altering water flow, soil pH and increasing sedimentation. Invading braided rivers, they provide cover for predatory pests hunting birds that nest on riverbeds, such as dotterels. The large appetites of rabbits and their burrowing habits have caused extensive loss of biodiversity and damage to pastoral land and grassland ecosystems. Soil has been stripped of organic matter, and irrigation properties and plants stripped of leaves and bark expose them to the elements and disease. The Cromwell chafer beetle (Prodontria lewisii) is now nationally endangered with an estimated population of 10,000 adults. The beetle's habitat has been degraded by rabbits, invasive plants and Redback Spiders (Latrodectus hasseltii), meaning they now only survive in reserves. Predation on birds, bats and reptiles by feral cats, stoats and rats has dramatically reduced native fauna populations in the region. The Grand skink (Oligosoma grande) and Otago skink (Oligosoma otagense) are now NZ’s rarest reptiles and are classified as Nationally Critically Endangered. They now only occupy 8% of their original habitat. Native fish and invertebrates have seen a significant population decline due to introduced fish (e.g.Trout), weeds (e.g Lagarosiphon major) and migration barriers (e.g Clyde Dam). The Clutha flathead galaxias (Galaxias 'species D') is now nationally critical, with a 35% loss over the last decade. Increasing sedimentation and changes to natural water flow have reduced spawning habitat availability. |
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Responsibilities
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The Otago Regional Council (ORC) is responsible for providing leadership to manage biosecurity issues and pest management strategies under the BioSecurity Act 1993. The ORC is involved in a variety of control programmes, such as wilding conifer and didymo control, and shares responsibility with many stakeholders, agencies and individuals.
The Ministry for Primary Industries (MPI) is the Government department that leads New Zealand’s biosecurity system. MPI administers the Biosecurity Act and undertakes surveillance of pests and diseases to prevent the introduction of new species. Land Information New Zealand (LINZ) manages 8% of NZ’s land area under The Crown. They own over 5,000 properties across New Zealand, totalling almost two million hectares. LINZ is responsible for biosecurity on land they manage and collaborate with other parties to combat pest species. |
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Management
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Removal of pest species, reintroduction of native species and protection of land is the only way to ensure our ecosystems and their biodiversity survive. Management is dependent on the species' individual behavioural and ecological characteristics as well as their impact on the environment. To prevent the cost of control from rising exponentially, swift and effective methods must be enforced. Collaboration with local authorities, landowners and community groups is needed to create a successful strategy that is specific to each location and pest.
In the case of rabbits, regular and assertive methods are needed. A combination of poisoning, fumigating and shooting can reduce and maintain low population numbers. However, all are labour-intensive, and costly and need the ORC to enforce pest control on landowners. Aquatic weeds such as Lagarosiphon are also incredibly difficult pests to remove from water bodies like Lake Dunstan. Various methods are used to control the growth of weed beds, each dependent on the characteristics of each location. Hand cutting, mechanical harvesting and herbicides are some of the methods used to control the weed but will not eradicate it completely. Aerial spraying with herbicide is an effective method for quick, precise and effective eradication of plants like wilding conifers that cover 1.8 million ha of NZ. Physically removing by cutting and digging is the best practice to remove plants like lupins and Broom. Once invasive pests are removed, the reintroduction of native plants will help improve the biodiversity of the area. Many of our flora and fauna are endemic and require specific habitats to survive. The survival of habitats is vital to ensure NZ does not lose any more amazing species like the South Island Poipoi, Aurora frog and short-tail bat. Establishing protected areas and reserves can ensure the continued management and improvement of native ecosystems. NZ has more than 10,000 protected areas, covering more than 8.6 million hectares (32% of the total land area). The Cromwell Chafer Beetle Nature Reserve is an example of how species and ecosystems can be saved. Established in 1983, the reserve aims to prevent extinction by protecting its habitat from pests and invasive plants. By focusing on ensuring the survival of one species, it indirectly protects other species which will occupy the same habitat. |
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What has been done
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In 2019, the ORC created a Biosecurity Strategy Plan to focus on 51 pest species that are threatening the environmental, economical and community well-being of the region. The plan outlined a strategy that is comprehensive of all funding and methods of control and eradication from all relevant agencies, stakeholders, landowners and community groups.
The MPI created the New Zealand Wilding Conifer Management Strategy in 2015 to collaborate with agencies, landowners and community groups to create a systemic, nationwide approach to pest control. Between 2016-2018 nearly 300,000ha of wilding conifers were cleared in Otago. Numerous local and national stakeholders, governing bodies and trusts have also created plans and legislations to improve biodiversity. In 2016 LINZ created the Lake Dunstan Weed Management Committee to implement a 10-year plan to control, manage and reduce Lagarosiphon in Lake Dunstan. Predator Free 2050 is a trust which collaborates with government agencies, the Department of Conservation, local communities, etc to outline a national strategy to eradicate animal pests by 2050. Locally, Lake Dunstan Charitable Trust (LDCT) and Mōhiki Reforestation Trust have pushed for the enhancement of Cromwell’s ecosystems both on land and in the surrounding water bodies. In March 2021, LDCT secured just under $1 million in funding from LINZ to enhance the shoreline’s wildlife and recreation by planting native species and removing pest species. Restoration of the shoreline will allow native plants, invertebrates and reptiles to return and improve education and mental well-being for the community. |
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What will be done
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The ORC’s Biosecurity Strategy Plan is focused on pressuring landowners to take more responsibility and improve pest control on their land. Pressure on landowners is needed as current management has not significantly reduced pests or their impact on the local environment.
The MPI Wilding Conifer Control in 2020-21 has a budget of $30 million with $5.5 million allocated to Queenstown and Otago to clear wilding conifers. Countrywide the budget will support 800,000ha of clearing and create 550 jobs. The National Institute for Water and Atmospheric Research (NIWA) is currently working with LINZ to research other possible solutions for Lagarosiphon. Such future methods could be biological control (animals who will eat the weeds), the use of different herbicides (e.g. endothall) and monitoring technologies to better map the lake bed. LDCT is looking to secure future funding to allow for continued improvements to Cromwell’s waterways and campaign for local landowners, government agencies and companies to uphold their legal obligations to improve and protect local biodiversity and ecosystems. |
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Kids activity sheets
Fun activity sheets for kids to identify native plants and animals along Lake Dunstan.
How many can they find?
How many can they find?
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References:
[1] Strategic Analysis of Options to Improve Management of Ecosystems and Biodiversity for Otago Region (2017). To view Click here
[2] Ecological Regions and Districts of New Zealand (1987). To view Click here
[3] S. Bryan (2014) An investigation into the abundance and ecological impact of Australian redback spiders (Latrodectus hasseltii) within and around the Cromwell Chafer Beetle Nature Reserve, Central Otago. To View Click here
[4] Growing Native Plants in the Wakatipu (2017). To view Click here
[5] S. Walker , W.G. Lee & G. Rogers (2004) The Woody Vegetation of Central Otago, New Zealand. To view Click here
[6] Otago Pest Management Plan 2019-2029 (2019). To view Click here
[7] DOC: Leonohebe cupressoides ('Fragrant hebe'). To view Click here
[8] DOC: Grand and Otago Skinks. To view Click here
[9] DOC: Clutha Flathead Galaxias. To view Click here
[10] NIWA (2016) Ten Year Management Plan for Lagarosiphon at Lake Dunstan: 2016 to 2025. To view Click here
[11] New Zealand Wilding Conifer Management Strategy 2015-2030. To view Click here
[12] ORC: Biosecurity Strategy (2019). To view Click here
[13] MPI: Wilding Conifer Control in NZ. to view Click here
Images: Unslash; DOC; DOC; DOC; NIWA
[1] Strategic Analysis of Options to Improve Management of Ecosystems and Biodiversity for Otago Region (2017). To view Click here
[2] Ecological Regions and Districts of New Zealand (1987). To view Click here
[3] S. Bryan (2014) An investigation into the abundance and ecological impact of Australian redback spiders (Latrodectus hasseltii) within and around the Cromwell Chafer Beetle Nature Reserve, Central Otago. To View Click here
[4] Growing Native Plants in the Wakatipu (2017). To view Click here
[5] S. Walker , W.G. Lee & G. Rogers (2004) The Woody Vegetation of Central Otago, New Zealand. To view Click here
[6] Otago Pest Management Plan 2019-2029 (2019). To view Click here
[7] DOC: Leonohebe cupressoides ('Fragrant hebe'). To view Click here
[8] DOC: Grand and Otago Skinks. To view Click here
[9] DOC: Clutha Flathead Galaxias. To view Click here
[10] NIWA (2016) Ten Year Management Plan for Lagarosiphon at Lake Dunstan: 2016 to 2025. To view Click here
[11] New Zealand Wilding Conifer Management Strategy 2015-2030. To view Click here
[12] ORC: Biosecurity Strategy (2019). To view Click here
[13] MPI: Wilding Conifer Control in NZ. to view Click here
Images: Unslash; DOC; DOC; DOC; NIWA
