Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.
Division of Plant Sciences, University of Dundee at the James Hutton Institute, Dundee, UK.
Nat Ecol Evol. 2022 Jun;6(6):675-683. doi: 10.1038/s41559-022-01722-1. Epub 2022 Apr 21.
Our scientific understanding of climate change makes clear the necessity for both emission reduction and carbon dioxide removal (CDR). The ocean with its large surface area, great depths and long coastlines is central to developing CDR approaches commensurate with the scale needed to limit warming to below 2 °C. Many proposed marine CDR approaches rely on spatial upscaling along with enhancement and/or acceleration of the rates of naturally occurring processes. One such approach is 'ocean afforestation', which involves offshore transport and concurrent growth of nearshore macroalgae (seaweed), followed by their export into the deep ocean. The purposeful occupation for months of open ocean waters by macroalgae, which do not naturally occur there, will probably affect offshore ecosystems through a range of biological threats, including altered ocean chemistry and changed microbial physiology and ecology. Here, we present model simulations of ocean afforestation and link these to lessons from other examples of offshore dispersal, including rafting plastic debris, and discuss the ramifications for offshore ecosystems. We explore what additional metrics are required to assess the ecological implications of this proposed CDR. In our opinion, these ecological metrics must have equal weight to CDR capacity in the development of initial trials, pilot studies and potential licensing.
我们对气候变化的科学认识清楚地表明，减排和二氧化碳去除（CDR）两者都必不可少。海洋因其巨大的表面积、深度和漫长的海岸线，是开发与限制升温至 2°C 以下所需规模相称的 CDR 方法的核心。许多拟议的海洋 CDR 方法依赖于空间放大，同时增强和/或加速自然发生过程的速率。一种这样的方法是“海洋造林”，它涉及近海藻类（海藻）的近海运输和同时生长，然后将其输出到深海。藻类在开阔海域停留数月，而藻类在开阔海域自然不会生长，这可能会通过一系列生物威胁影响近海生态系统，包括改变海洋化学性质和改变微生物生理和生态。在这里，我们对海洋造林进行了模型模拟，并将这些模拟与其他近海扩散的例子（包括漂浮塑料碎片）的经验教训联系起来，讨论了对近海生态系统的影响。我们探讨了评估拟议的 CDR 对生态影响所需的其他指标。在我们看来，在初始试验、试点研究和潜在许可的开发中，这些生态指标必须与 CDR 能力具有同等权重。
