Logs or permits? Forestry land use decisions in an emissions trading scheme

Negative carbon emissions options are required to meet long-term climate goals in many countries. One way to incentivise these options is by paying farmers for carbon sequestered by forests through an emissions trading scheme (ETS). New Zealand has a comprehensive ETS, which includes incentives for farmers to plant permanent exotic forests. This research uses an economy-wide model, a forestry model and land use change functions to measure the expected proportion of farmers with trees at harvesting age that will change land use from production to permanent forests in New Zealand from 2014 to 2050. We also estimate the impacts on carbon sequestration, the carbon price, gross emissions, GDP and welfare. When there is forestry land use change, the results indicate that the responsiveness of land owners to the carbon price has a measured impact on carbon sequestration. For example, under the fastest land use change scenario, carbon sequestration reaches 29.93 Mt CO2e by 2050 compared to 23.41 Mt CO2e in the no land use change scenario (a 28% increase). Even under the slowest land use change scenario, carbon sequestration is 25.89 Mt CO2e by 2050 (an 11% increase compared with no land use change). This is because, if foresters decide not to switch to permanent forests in 1 year, carbon prices and ultimately incentives to convert to permanent forests will be higher in future years.

为达成多国长期气候目标，负碳排放方案不可或缺。激励此类方案的途径之一，是通过排放交易体系（Emissions Trading Scheme, ETS）向农民支付森林固碳相关费用。新西兰拥有一套全面的ETS，其中包含鼓励农民种植永久性外来森林的激励措施。本研究结合经济全域模型、林业模型及土地利用变化函数，测算2014至2050年间新西兰境内，处于采伐龄的农户中将生产用地转为永久性森林的预期比例；同时评估该转变对碳固存、碳价、总排放量、GDP及社会福利的影响。结果显示，当存在林业用地转换时，土地所有者对碳价的响应程度会显著影响碳固存效果：例如，在最快用地转换情景下，2050年碳固存可达29.93 Mt CO₂e，较无转换情景的23.41 Mt CO₂e提升28%；即使在最慢转换情景下，2050年碳固存仍达25.89 Mt CO₂e，较无转换情景增长11%。这一现象的原因在于：若林农在某一年未选择转为永久性森林，未来的碳价及转换激励力度将进一步提高。