Why are we doing this?
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In our region current vegetation cover in hill country areas comprises pasture (70%), exotic forest (20%), indigenous forest (6%), and bare ground (4%). Before Māori (~600 yr BP) and European (commencing in the 1820s) settlement, the East Coast region was almost completely vegetated with podocarp / hardwood (mainly conifer) forest in the lowlands, Nothofagus forest at higher altitudes, and alpine-subalpine shrub land and grasslands on the highest parts of the axial ranges. Deforestation of the watershed, primarily by burning, commenced in its lower reaches with the arrival of Polynesian (Māori) settlers around 700 years ago and extended into the headwater reaches following European settlement. Much of the lowland had been deforested by 1875 and by the late 1920s 97.5 % of the old-growth native forests had been destroyed. The combination of highly erodible, steep and jointed bedrock, tephric soils and alluvium, episodically intense precipitation, seismic activity, and human disturbance contribute to rapid erosion of the Waipaoa watershed, and one of the highest suspended sediment yields in the world.
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Within a reforested area any measured reduction in ‘active’ eroded area of individual shallow landslides, earthflows, and gullies is attributed to increasing tree canopy size over time. A closed canopy by inference, implies the erosion feature has stabilised. The present day sedimentation problem in the Waipaoa catchment is of historical origin and can be attributed directly to the dramatic increase in hill slope erosion following clearance of the indigenous forest from erosion-prone terrain during the early European settlement period. Following reforestation, streams within mature plantation forests have greater stability and lower water temperature than adjacent pastoral streams, resulting in improved overall stream ecological health approaching the condition of reference streams in native forest. Reductions in sediment input and improvements in stream health are possible at a localised scale and within a relatively short time frame but are unlikely to make a significant difference to the sediment load or water quality of the Waipaoa River as a whole for many decades, if not millennia.
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Without further erosion mitigation intervention and in the event of more severe storm events, erosion on unprotected hill slopes will increase and further exacerbate the current sedimentation issues of the Waipaoa catchment. The impacts of pre- or post-European deforestation have persisted for more than a century. Climate change is likely to exacerbate erosion problems and lead to increased sedimentation since it is predicted to cause heavier and/or more frequent extreme rainfalls. Reference: Sedimentation History of Waipaoa Catchment Envirolink project 1015-GSDC96 Mike Marden, Landcare Research |
Our Tohu
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At a number of recent whānau hui a map of the our broader Māhaki and Ngariki whenua that identified sites of hapū significance and in particular papakainga (1930-1950; 1950 -1975/1980s) of all of the whānau living in and around these places of significance was re-constructed. Alongside this reconstruction there were stories to contain relationships of and between our people and the land. Whānau talked about pā sites, urupā, rivers and streams, local swimming holes, where tuna-rua/hiringa were, watercress patches, orchids, kūmara pits and places for gathering rongoa, the weaving that happened and who those were, and the birds to listen out to for harvesting time and so forth and, that identified changes and losses in time.
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