Botanical Survey of the Hauraki Gulf Islands
Pakatoa with Rotoroa Island behind, from Stony Batter, Waiheke Island, Jan 2010
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Ewen Cameron, Auckland Museum’s Curator of Botany, recently led a botanical survey of wild (native and naturalised) plants of the Hauraki Gulf Islands.
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Assisted by botanical colleagues and members of the Auckland Botanical Society the field work included a chain of mainly privately owned islands east and southeast of Waiheke Island: Tarahiki, Pakatoa, Rotoroa, “Ruthe Islet” (between Rotoroa and Ponui Islands), Ponui, Pakihi, and Karamarama Islands.
Many unusual or interesting vascular plant records (natives and weeds) were collected, pressed and added to the Museum’s herbarium as a permanent record. Before these surveys most of these islands floras were poorly or totally unknown. Searches were carried out for any existing historical records held in New Zealand herbaria to indicate what may have occurred before – only a few were found. The earliest collection from any of these islands appears to be by Donald Petrie in 1894 from Rotoroa Island.
The number of species present was generally related to area, and the native percentage was strongly related to disturbance, e.g. Karamarama Island is a commercial chert quarry and only 29% of its flora was of native species, whereas “Tarahiki and “Ruthe Islet” had complete native forest canopies and a flora 65-66% of native species. Ponui Island contained the most diverse forest, but the naturalised species in the pasture were probably under-recorded, hence the 66% of native species might be slightly inflated.
The future changes on these islands can be measured against these base-line surveys which are all published in the Auckland Botanical Society Journal, vols. 47, 55, 60, 61, 62, 65 and available online (except 65) at: http://bts.nzpcn.org.nz/.
Wild plant totals in different groups, area, maximum height and proximity to a larger island for the seven islands east and south east of Waiheke Island: |
Plant Group |
Tarahiki |
Pakatoa |
Rotoroa |
“Ruthe Islet” |
Ponui |
Pakihi |
Karama-
rama |
Totals |
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Native ferns & fern allies |
14 |
17 |
26 |
8 |
75 |
28 |
3 |
81 |
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Native conifers |
- |
- |
1 |
- |
8 |
- |
- |
8 |
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Native dicots |
51 |
57 |
99 |
49 |
112 |
77 |
18 |
147 |
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Native monocots |
27 |
22 |
48 |
16 |
85 |
50 |
7 |
104 |
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Native sub total |
92 |
96 |
174 |
73 |
280 |
155 |
28 |
340 |
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Naturalised fern & fern allies |
- |
1 |
2 |
- |
- |
- |
- |
2 |
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Naturalised conifers |
- |
3 |
4 |
1 |
3 |
3 |
1 |
5 |
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Naturalised dicots |
30 |
88 |
153 |
23 |
96 |
102 |
47 |
221 |
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Naturalised monocots |
20 |
25 |
65 |
14 |
45 |
44 |
22 |
84 |
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Naturalised sub total |
49 |
117 |
224 |
38 |
144 |
149 |
70 |
312 |
Overall totals |
142 |
213 |
398 |
111 |
424 |
304 |
98 |
652 |
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% native |
65 |
45 |
44 |
66 |
66 |
51 |
29 |
52 |
Area, height, & distance to a larger island |
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Area (ha) |
5.9 |
29.3 |
90.0 |
0.6 |
1795 |
114 |
7.3 |
[2042] |
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ASL (m) |
68 |
60 |
76 |
20 |
173 |
125 |
20 |
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Prox. to a larger island (km) |
2.5 |
0.7 |
0.9 |
0.2 |
1.3 |
1.3 |
0.4 |
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