Latest lakeshore vegetation survey and an update on willow control

Transcription

1 Latest lakeshore vegetation survey and an update on willow control Jodi Rees Environment Canterbury Te Waihora Living Lake Symposium, 9 10 November 2017, Lincoln University Photo: Alice Shanks April 2017 Key messages Overall the state of lakeshore wetland vegetation has improved over the last ten years. However: Exotic willows and other weeds continue to pose a threat to indigenous vegetation, particularly freshwater wetland habitats Damage to, or removal of, indigenous lakeshore wetland vegetation has occurred in the last ten years (mechanical clearance and herbicide) Grazing of the lake edge wetlands by sheep and/or cattle continues along more than half of the lake shore Vehicle damage to native saltmarsh vegetation on Public Conservation Land continues to be a problem

2 Context and objectives Monitoring of vegetation around the margin of Te Waihora is carried out through repeated surveys, mapping, and description of lakeshore habitats Allows reporting on the following measures of success: Annual net gain of key habitats (e.g. raupō) and maintenance of other important habitat types (e.g. saltmarsh) Maintain or increase populations of threatened or at risk plant species Annually reduce and stop spread of key problem willow species and other significant animal and pest weeds of native vegetation Methods lakeshore vegetation survey Previous surveys in 1983 and 2007 Survey took place in early 2017 and covered the entire lakeshore of Te Waihora Mapping units (polygons) were delimited on recent large scale colour aerial photographs Vegetation was described following accepted standards for structural classes, species composition and relationships Mapping units were entered into a GIS shape file, clipped to ensure comparison of same geographic extent Comparisons made to previous survey data

3 Methods willow control Weed and willow control around the lakeshore is guide by a strategy Weed led or site led Control takes place either by aerial spraying from a helicopter (for dense infestations of grey willow in larger areas), or targeted ground work It is funded through the Regional Committee s Te Waihora Flagship and the Whakaora te Waihora program, in partnership with landowners and the Department of Conservation Lakeshore vegetation survey native species Photo: Alice Shanks April 2017

4 Lakeshore vegetation survey threatened species Photo: Alice Shanks March 2017 Lakeshore vegetation survey threatened species Photo: Alice Shanks March 2017

5 Lakeshore vegetation survey threatened species Photo: Philip Grove February 2017 Lakeshore vegetation survey weeds Existing weeds have become more common outside of targeted control areas 9 new weeds recorded since last survey

6 Te Waihora willow mapping Willow infestation by cover class Occassional willows Sparse willows Scattered willows Moderate infestation Dense infestation Close canopy willow forest

7 Photo: Mark Parker April 2017 Harts Creek Wildlife Management Reserve willows

8 Photo: Vicki Meyer August 2017 Photo: Philip Grove March 2017

9 Photo: Philip Grove April 2017 Photo: Philip Grove March 2017

10 Photo: Robin Smith November 2016 Photo: Jodi Rees November 2016

11 Vehicle Damage Vehicle Damage

12 Vehicle Damage Implications: Opportunities for strategic weed control of new/isolated infestations More fencing = increased management of willows in freshwater wetlands where grazing has been retired Grey willow control needs to step up to keep pace with colonisation (especially in raupō Australasian bittern habitat)

13 Acknowledgements Dr Philip Grove, Mark Parker, Mirella Pompei Environment Canterbury Craig Alexander, Robin Smith Department of Conservation Alice Shanks Independent Botanist