BY: DR KEN GEENTY
The often-held view that greenhouse gases (GHGs) from sheep and beef cattle contribute to climate change is being questioned.
A recent study, supported by Beef + Lamb NZ (B+LNZ) and led by Dr Bradley Case at the Auckland University of Technology, found up to 90% of GHG emissions from livestock are absorbed by woody trees on farms.
This implies carbon neutrality meaning GHGs emitted are cancelled out by a similar amount of absorption. The CO2 is gobbled up by growing woody trees and incorporated as plant storage via photosynthesis.
The insatiable appetite of trees for carbon is highlighted in a recent Nature Journal article on climate change. It pointed out that our famous native forests, often adjacent to farming areas, are an enormous carbon sink. Nationally they hold some 7 billion tonnes of CO2 that would normally be in the atmosphere. This GHG storage is equivalent to about 86 years of NZ’s total emissions.
Although generally slow growing, most native trees are not eligible for our Emissions Trading Scheme (ETS) but they collectively make a very significant contribution to GHG mitigation. Some natives planted after 1989, on what is classed as ‘forest land’ under the ETS, are eligible.
Not surprisingly tree planting on farms is gaining momentum. Of 8.5 million hectares of sheep and beef farms it is estimated the 1.7m ha in trees will grow to 2m ha by 2028. Some argue a large proportion of these plantings are pine monocultures, destined for the timber industry, often with detrimental environmental and farming consequences.
With about 40m sheep, cattle and deer NZ is one of the most densely populated countries in the world with farm animals. It’s estimated that some 44% of our national greenhouse gases are emitted as methane from burping ruminants. However, the recent research showing trees on sheep and beef farms absorb a big proportion of these emissions means farms are closer to being carbon neutral with no net increase in GHGs than previously thought.
Methane emitted by animals is a potent greenhouse gas with one ton having the equivalent of 25t of carbon dioxide. The less significant but highly potent nitrous oxide comes from dung fermentation. These gases, along with carbon dioxide, damage the protective ozone barrier near our stratosphere contributing to global warming.
Sea level rises and adverse weather events are the well known consequences of climate change.
Under the 2015 Paris Agreement our government pledged to reduce greenhouse gas emissions by 30% below 2005 levels by 2030. Subsequently an Independent Climate Change Commission (ICCC) began working towards NZ wide carbon neutrality by 2050. Legislation soon to be passed is labelled by Prime Minister Jacinda Ardern as ‘ground-breaking’. B+LNZ has voiced support and agreement to help ICCC ensure the framework operates effectively at farm level.
Farming contributions are gaining momentum with a primary sector action partnership on climate change, embracing B+LNZ, DairyNZ, Deer Industry NZ and Federated Farmers, looking at various options such as incorporating vegetation not eligible under the ETS.
The NZ ETS administered by the Ministry of Primary Industries (MPI) to reduce impacts of GHGs on climate change is available to farmers. More information can be found on https://www.mpi.govt.nz under the heading ‘About the Emissions Trading Scheme’.
For carbon credits under the ETS, farm forestry needs to be specifically for greenhouse gas mitigation and not for eventual timber production. If eligible trees are subsequently felled for clearing or for timber carbon credits need to be repaid.
Longevity for ETS ranges from 50 to 100 years for pines, cypresses, and eucalypts and more than 100 years for many natives. Costs to prepare for ETS participation include initial preparation and planting, a start-up fee, maintenance including pruning, thinning and fencing and annual returns to MPI.
Tree planting can include marginal areas on farms and at least 30 metre wide riparian strips protecting waterways. With 42ha of growing trees mitigating equivalent emissions from some 700 ewes or 100 cows, large areas of trees are needed for carbon neutrality. This is changing the face of much of our hill country farming areas. However, to date only a tiny proportion of our national forests are in the ETS with about 323,032ha from 2047 land-owner participants, about 1700 of which are farmers. There are 702,590ha of eligible forest land.
Horowhenua farmers Marlene and Patrick Anderson are early adopters on their steep 800ha property in the Tararuas near Shannon. Their conservation-motivated emissions plan sees 70ha in planted pines and 90 in regenerated natives. These trees annually mitigate between four and 25t of carbon dioxide per hectare earning just over half of the Andersons’ previous farm income. About 200ha is devoted to grazing 400 sheep while the balance is retired land with mature pines and native bush.
Even though their farm is atypical with a high proportion of the land in trees, the Andersons’ farm is great example of what can be done by combining conservation with the ETS.
Marlene and Patrick say the MPI-administered emissions scheme is flexible and easy to run. Trading credits through a broker is a same-day service. The farm has scope to develop further areas with eucalypts as ‘nursery trees’ earning carbon credits with native bush regenerating underneath. They want to avoid monocultures on their idyllic bush-clad holding.
This concept of mixed plantings not only beautifies the landscape but encourages healthy biodiversity.
Even though the ETS and tree planting on farms aims at mitigation of existing animal emissions there are also opportunities to reduce emissions. The Pastoral Greenhouse Gas Research Consortium says options for reduction include:
- Breeding low-emitting sheep and cattle
- Providing low methane-emitting feeds and additives
- Use of methane-reducing vaccines.
One or more of the above options could reduce GHG emissions by up to 20% and the technology will be increasingly available within the next five years. An early start has seen a “methane research breeding value” available from B+LNZ Genetics to breed animals emitting less methane.
More information about strategies to reduce GHG emissions on farms can be found on the B+LNZ website at beeflambnz.com/search?term=greenhouse+gases
Some management alternatives for reducing animal emissions coming from the Biological Emissions Reference Group (BERG) include reduced stocking rates with increased per head production and lower fertiliser applications. BERG say that sheep and beef farms have made a good start with 30% less emissions over the past 25 years.
Sheep and beef farmers are very much doing their bit to lessen animal emissions impacts on climate change.
- Ken Geenty is a primary industries consultant.
