Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth John Innes1, Florian V. Eppink2 Landcare Research Hugh Robertson3 Department of Conservation Prepared for: Kiwis for kiwi / The Kiwi Trust Private Bag 68908 Auckland 1145 July 2015 1Landcare Research, Gate 10 Silverdale Road, University of Waikato Campus, Private Bag 3127, Hamilton 3240, New Zealand, Ph +64 7 859 3700, Fax +64 7 859 3701, www.landcareresearch.co.nz 2Landcare Research, 231 Morrin Road, St Johns, Private Bag 92170, Auckland 1142, New Zealand, Ph +64 9 574 4100, Fax +64 9 574 4101 3Department of Conservation, P.O. Box 10420, Wellington 6143, New Zealand Reviewed by: Approved for release by: Roger Pech Suzie Greenhalgh Scientist Portfolio Leader - Enhancing Policy Development Landcare Research Landcare Research Landcare Research Contract Report: LC2136 Disclaimer This report has been prepared by Landcare Research for Kiwis for kiwi. If used by other parties, no warranty or representation is given as to its accuracy and no liability is accepted for loss or damage arising directly or indirectly from reliance on the information in it. Contents Executive summary ..................................................................................................................... v Glossary of key terms ................................................................................................................. vi Summary ................................................................................................................................... vii 1 Introduction ....................................................................................................................... 1 2 Background ........................................................................................................................ 2 3 Objectives .......................................................................................................................... 2 4 Modelling kiwi recovery strategies ................................................................................... 2 4.1 Overview .............................................................................................................................. 2 4.2 Kiwi taxa and estimated 2015 population sizes .................................................................. 3 4.3 Current kiwi threats and management regimes, and resultant estimated population growth rates ........................................................................................................................ 5 4.4 Modelling halting the decline and achieving 2% per annum growth ................................ 14 5 Estimating current and additional cost ........................................................................... 19 5.1 Cost data considerations ................................................................................................... 19 5.2 Annual cost of current management ................................................................................ 22 5.3 Additional cost of population stability and growth targets .............................................. 23 6 Discussion ........................................................................................................................ 31 6.1 Adequacy of input kiwi data .............................................................................................. 33 6.2 Kiwi modelling assumptions .............................................................................................. 33 6.3 Selecting growth scenarios and preferred management techniques ............................... 33 6.4 Community conservation and cost modelling ................................................................... 34 6.5 Additional funding required to halt declines and achieve 2% growth p.a. ....................... 35 6.6 Priority research and monitoring ...................................................................................... 36 7 Acknowledgements ......................................................................................................... 36 8 References ....................................................................................................................... 37 Landcare Research Page iii Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth Appendix 1: Explanation of key terms in this report ............................................................... 40 Appendix 2: Cost data and assumptions .................................................................................. 42 Page iv Landcare Research Executive summary Kiwi conservation has been very successful since the Kiwi Recovery Programme was launched in 1991. Much has been learned about kiwi and their threats; some tools have been developed to grow kiwi populations; there is a groundswell of community and political support to keep kiwi safe, and populations of the four rarest kiwi taxa are increasing. However, substantial additional effort is required to reverse the overall potential decline of 2% per annum (without management) into a 2% increase across all 10 taxa (‘kinds’ of kiwi). With the assumptions that kiwi conservation projects run by community groups ($6.3 million of funded and donated costs) and by the Department of Conservation (DOC) remain at current levels, and with new government funding of $6.8 million per year from 2018 onwards as announced in Budget 2015, we estimate that all 10 kiwi taxa can be at least maintained at current population levels. By our best modelled estimates, a further ca $1.3 million per year is required across all kiwi to achieve an average of 2% per annum growth per year between now and 2030. Using DOC staff instead of community volunteers, more aerial poisoning, and allocating pest-fence costs to kiwi recovery will increase the estimated funding need. Nationally, major challenges ahead include: a) reversing declines of those more abundant, but steadily declining, kiwi taxa that live in remote and rugged parts of the South and Stewart Islands, where human populations are small and remote from kiwi populations, and b) cost- effectively monitoring the outcomes of management for all kiwi. Landcare Research Page v Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth Glossary of key terms Kiwi taxa (plural) and taxon (singular): For simplicity, we refer to the 10 different ‘kinds’ of kiwi (e.g. little spotted, Northland brown) as taxa, even though some are not taxonomically described in scientific literature. Management regime: There are seven active management regimes, such as pest trapping, aerial poisoning or Operation Nest Egg, that are applied to kiwi populations to increase their numbers. Population growth rates: Kiwi populations are subject to annual change, depending on nett outcomes of births and immigration versus deaths and emigration. We express change rates either as (for example) 2% p.a. (so that each year the population is 2% larger), or for modelling purposes, as 1.02. There may also be 2% p.a. declines, which we express for modelling as 0.98. Modelling parameters: Population modelling in this report uses (for each taxon) an initial population size and subsequent growth rates that may differ for each management regime, but population size and growth rates are both imperfectly known. Therefore, we model these possible errors by choosing between most likely, or high and low (e.g. ±30%) values of modelling parameters. Conservation scenarios: These are combinations of management regimes that in aggregate achieve a desired population growth rate (e.g. 2%) target. All seven management regimes can be mixed to create a large number of different conservation scenarios, with different outcomes for the kiwi populations, and different costs. Page vi Landcare Research Saving a national icon: Preliminary estimation of the additional cost of achieving kiwi population stability or 2% growth Summary Client and Project Kiwis for kiwi (The Kiwi Trust, K4K) asked Landcare Research to estimate the likely cost of achieving 2% population growth of all 10 accepted and perceived taxa of kiwi, given that unmanaged populations are estimated to be declining at 2% per annum. Due to limited availability of input data, this project estimates the cost of the additional (to current) management required to halt declines or increase populations at 2% per annum for only the kiwi taxa not already meeting these targets. It does not estimate the total cost of achieving 2% population growth for all 10 kiwi taxa. Objectives To determine additional management so that all 10 kiwi taxa will a) stop declining, or b) increase by 2% per annum. To estimate the costs of this additional management. Methods For all 10 kiwi taxa, we first estimated the 2015 population size, and then allocated all individuals to one of seven management regimes, each with its own estimated annual population change rate. We then estimated the resultant, nett change rate after 1 year and after 15 years for each taxon’s population, considering all regimes. For each taxon failing to achieve 0% or 2% growth under current management, we then modelled increasing the number of kiwi subject to predator management, until the nett change rate