Fact Files
» Soil Carbon» New Zealand's major greenhouse gases
» New Zealand's unique greenhouse gas emissions profile
» Offsetting Carbon Dioxide Emissions & Ebex21®
» Global response to Climate Change
Soil Carbon
The world's soils contain very large amounts of carbon, more than resides in the vegetation and atmosphere combined! Although some of this carbon is found in charcoal or coal fragments, most of it occurs in soil humus where it forms the skeleton to bind soil particles, hold plant nutrients, and provide food for micro-organisms. Carbon levels in soil organic matter represent a balance between additions from plant residues, and losses from decomposition (rotting) by these micro-organisms.
Simple Carbon Cycle
Any disturbance, either natural (e.g., some types of erosion) or by humans (e.g., tillage for cropping) causes carbon to be lost or gained as this balance is shifted. If more carbon is added by increased plant residue input then soil carbon will gradually increase. If inputs are reduced by changing land use or management, then soil carbon will decline, and extra carbon dioxide will be released to the atmosphere. Because so much carbon is stored in soil, even small changes in the plant reside inputs or decomposition can have a large effect on the carbon dioxide levels in the atmosphere. Erosion can also change soil carbon levels, but this is mainly from direct removal of the soil from the land to rivers and the sea.
In New Zealand, much of our soil carbon is stored in organic matter beneath grazed pastures where it is maintained at high levels by efficient transfer of carbon to soil from roots. If these soils are cultivated, for example, there is a rapid loss of soil carbon (releasing much carbon dioxide into the atmosphere). This occurs for several years, and is largely due to the much lower inputs from crops compared to pastures. Loss of soil carbon also occurs when pines are planted into pastures, or scrub grows on former pastures although losses are much smaller than for crops.
Most New Zealand pastures are well stocked with soil carbon and there is little scope for increases-indeed there is evidence that soil carbon can decline if already fertile pastures receive more fertiliser. In general however, fertiliser additions enhance plant residue inputs and decomposition, so cycling of carbon increases, but soil carbon levels remain at a steady state. This is why we cannot use soils to store more carbon to offset methane and nitrous oxide emissions from New Zealand farms.
For further information, contact: Kevin Tate, Surinder Saggar
Read more about our research on estimating New Zealand's soil carbon: Accounting for New Zealand's carbon
New Zealand's Major Greenhouse Gases
Carbon Dioxide
Carbon dioxide (CO2) is released to the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned. CO2 is a major greenhouse gas because of the huge amounts produced- the United States alone produces over 1,500 million tonnes per year.
CO2 accounts for almost 40% percent of New Zealand's greenhouse gas emissions. Transport is a major source of CO2 emissions in New Zealand.
CO2is the reference gas against which the "greenhouse effect" or global warming potential of other greenhouse gases is measured. CO2 has a global warming potential of 1.
Methane
Methane is produced in the rumen of sheep and cattle, and is New Zealand's major greenhouse gas (accounting for over 40% of New Zealand's greenhouse gas emissions). Methane is also a byproduct of decomposition of organic wastes, rice production and production of coal, natural gas, and oil. It also occurs naturally-sources include wetlands, termites, oceans, and gas hydrate nodules on the sea floor.
The atmosphere is the major sink for CH4, but some CH4 is also consumed by soil organisms (methanotrophs).
Annual global production of methane is 400 to 600 Tg (1Tg=1 million tonnes), which is equivalent to 8,400-12,600 Tg of CO2. A 1995 study estimated that human activity was the cause of 60% of methane emissions to the atmosphere.
New Zealand's methane emissions are over twice the global average because of New Zealand's largely agricultural-based economy.
Methane is a more potent greenhouse gas than carbon dioxide. It has a global warming potential of 21.
Nitrous Oxide
Nitrous oxide (N2O) is emitted from various activities including agricultural production and industrial activities, as well as combustion of solid waste and fossil fuels. It is produced by microorganisms in the soil, and emissions are higher when soils are wet.
N2O is New Zealand's most potent greenhouse gas. N2O accounts for about 16 percent of New Zealand's greenhouse gas emissions.
N2O is a much more potent greenhouse gas than CO2. It has a global warming potential of 310.
New Zealand's Unique Greenhouse Gas Emissions Profile
New Zealand's total greenhouse gas (GHG) emissions are small from a global perspective (around 0.5% of global emissions). However, among developed countries New Zealand has a unique GHG emissions profile (Figure 1). Because New Zealand's economy is based largely on agriculture, methane from animal production accounts for approximately 50% of the country's total emissions. In other developed countries, carbon dioxide is the major greenhouse gas produced.
Figure 1. Diagram showing New Zealand's unique greenhouse gas emissions, and global emissions profile.
New Zealand submits an annual greenhouse gas inventory to the United Nations Framework Convention on Climate Change (UNFCCC). Greenhouse gas emissions and sinks for 1990 and 2000, reported in 2001, are shown in Table 1. All figures are kilotonnes of carbon dioxide equivalents*.
* The CO2 equivalent for a gas is derived by multiplying the amount of the gas produced by its Global Warming Potential (GWP). The GWP is a factor that represents the relative potency of each gas, i.e. its relative contribution to the greenhouse effect.
Global response to Climate Change
Public interest in environmental issues grew rapidly during the 1980s. Governments grew increasingly more aware of climate-related impacts and issues, including the strong scientific evidence that human activity is resulting in increased greenhouse gas emissions. In 1988 the United Nations General Assembly adopted a resolution to protect the global climate for present and future generations.
Global initiatives -IPCC and UNFCCC
In the same year (1988) the Intergovernmental Panel on Climate Change (IPCC) was formed to assess available scientific information on climate change. The IPCC's First Assessment Report, issued in 1990, confirmed that climate change posed a significant threat to our environment. Negotiations on a convention on climate change were formally launched, and at the United Nations Conference on Environment and Development (the "Earth Summit") in Rio de Janeiro in June 1992, the new Convention-the United Nations Framework Convention on Climate Change (UNFCCC)-came into being.
Objective of the United Nations Framework Convention on Climate Change
". . . to achieve stabilization of atmospheric concentrations of greenhouse gases at levels that would prevent
dangerous anthropogenic (human-induced) interference with the climate system . . ."
The UNFCCC set out a framework for intergovernmental efforts to tackle climate change. It established an objective and principles, and outlined commitments for different countries according to their circumstances and needs. It also provided guidelines to enable governments to monitor efforts to implement the Convention and to share insights on how best to pursue the Convention's aims.
Parties to the UNFCCC meet annually at the Conference of the Parties, (known as the COP) to continue talks on how best to tackle climate change, and to decide on rules that will facilitate practical and effective implementation of the Convention. At the 3rd meeting-COP 3-in Kyoto, Japan, in December 1997, a substantial extension to UNFCCC was adopted. This was the Kyoto Protocol.
Stronger commitment-the Kyoto Protocol
The Kyoto Protocol outlines legally binding commitments. It requires formal signature and ratification by governments. A protocol is an international agreement that stands on its own, but is linked to an existing treaty. The Kyoto Protocol therefore shares the objectives of the UNFCCC, but it builds on those objectives by adding new commitments that are stronger and more complex than those in the Convention. The Kyoto Protocol recognises, and responds to, the huge challenges posed in attempting to control of greenhouse gas emissions, and the diverse political and economic interests of participating countries.
The Protocol sets binding targets for countries to achieve emissions reductions or to take responsibility for excess emissions. Mechanisms for dealing with excess emissions include buying Emission Units internationally, using sink credits, and participating in emission reduction projects in other countries. To date, a number of countries have ratified the Protocol.
However, before the Protocol can to come into force at least 55 Parties to the Convention must ratify, including enough "Annex 1" parties to account for 55% of the group's carbon dioxide emissions (1990 levels). (Annex 1 countries include industrialised countries that were members of the Organisation for Economic Development and Cooperation (OECD) in 1992, and countries such as the Russian Federation whose economies are in transition).
Because the Kyoto Protocol will affect most major sectors of the economy, it is considered the most far-reaching agreement on environment and sustainable development ever adopted.
For more information on UNFCCC and the Kyoto Protocol, see:
Caring for climate: a guide to the Climate Change Convention and the Kyoto Protocol (UNFCCC)
http://unfccc.int/resource/cfc_guide.pdf (1.6Mb)
Offsetting Carbon Dioxide Emissions & Ebex21®
Plants grow by converting light energy, through photosynthesis, into chemical forms of energy that can be used by the plant. During photosynthesis, atmospheric CO2 is absorbed by plant leaves, carbon from CO2 is incorporated (sequestered) into various carbon-based plant components such as wood, and oxygen is released into the atmosphere. Because photosynthesis consumes atmospheric CO2, significant areas of indigenous or planted forest can offset some of the CO2 emissions produced by human activities.
Landcare Research's EBEX21®programme works with businesses and landowners to measure, manage and mitigate CO2 emissions. Landcare Research also offsets some of the CO2 emissions produced by its own activities by increasing carbon stored in native vegetation.
We achieve this by increasing our ownership of carbon credits (EBEX21®CO2units) from land reverting to indigenous forests. Landcare Research now owns units from 120 hectares of land, enabling us to offset 600 tonnes of CO2 emissions per year. We will continue purchasing units to progress toward our target of zero net emissions of greenhouse gases by December 2005.