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A new Forest & Bird report gives a stark warning that ongoing damage by introduced browsing pests causes native habitats to bleed stored carbon.  

The report, Protecting our Natural Ecosystems’ Carbon Sinks, reveals the West Coast’s kāmahi-podocarp forests alone are presently bleeding 3.4 million tonnes of CO2 every year because of browsing from deer, goats, chamois, and possums. To put this carbon loss into perspective it is equivalent to the country’s 2018 domestic air travel emissions.  

The report also estimates controlling these feral browsing pests to the lowest possible levels would increase the carbon sequestration of native ecosystems by 8.4 million tonnes of CO2 per year, which is equivalent to nearly 15% of New Zealand’s 2018 net greenhouse gas emissions. 

“The possums, deer, wallabies, goats, pigs, chamois, and tahr that were released into the wild have been chomping their way through native forests, shrublands, and tussocklands,” says Forest & Bird Chief Executive Kevin Hague.

“This has destroyed the natural ability of native ecosystems to be the best carbon sinks on land.”  

“Our native ecosystems in their natural state are superb at locking in and storing vast amounts of carbon. But they need to be healthy and free from introduced animal pests to do that.”   

“The range of browsing pests are out of control across the country with both deer and goat numbers increasing significantly over the past decade.”   

“When native forests collapse, huge volumes of carbon dioxide are released as trees die and rot. Our largest forest type, kāmahi-podocarp forest, is presently bleeding 3.4 million tonnes of CO2 every year,” says Mr Hague. 

“Impacts are multiplied if more than one invasive species of browser is present. Together, they are killing our native habitats and causing native forests, shrublands, and tussocklands to release carbon instead of holding it. By eating seedlings and killing young trees these introduced pest animals also consume future generations of forest, and our future carbon sinks.” 

“Acting now to turn around the destruction caused by browsing pests would restore natural carbon sinks and protect native plants and wildlife.”  

“This work needs to be over and above New Zealand’s climate commitments to eliminate fossil fuel emissions and substantially cut agricultural emissions as part of our fair share of global efforts to help keep warming below 1.5 degrees. It could even help make Aotearoa carbon positive within a few decades.”  

Forest & Bird is calling for increased control, coordination, and research to reduce browsing pests, and restore the carbon sequestration of native ecosystems.   

“Healthy native habitats are our biggest ally in the fight against climate change.” 

“Also, farmland that is currently being retired and allowed to regenerate as well as newly planted permanent native forest sinks will need protection from browsing mammals too or all that work will be wasted,” says Mr Hague. 

Summary of recommendations from Forest & Bird report:    


  • Significantly reduce the number of introduced browsing species (goats, possums, deer, wallabies, chamois, and tahr) in Aotearoa for the win-win outcome of both native species protection and carbon sinking abilities of native forests, shrublands and tussocklands.  
  • Prioritise control where evidence shows forests are losing a significant amount of stored carbon, such as kāmahi-podocarp forests.    


  • Coordinate predator control (rats, possums, stoats, feral cats) with browser control (goat, deer, wallabies, chamois, tahr), so whole native ecosystems can recover and be the best carbon sinks on land.   
  • Support more sustained and coordinated control of introduced feral browsers on public and private land to prevent spread and reinvasion.   


  • Substantially increase the number of forest plots that are regularly measured to better detect changes in forest carbon stocks and the response to pest control. Provide greater resources to ensure the results of this work are rapidly available to guide management to maximise carbon storage.  
  • New technologies for introduced browser control.   

To read the full report, visit: 

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