I was filled with hope when I read the first draft of the Global Biodiversity Framework (GBF) in mid-2021. It seemed that the parties to the United Nations Convention on Biodiversity had learnt from bitter experience — the failure of the Aichi Biodiversity Targets, set for the previous decade. Instead of vague aims, the draft framework incorporated most of the advice that the scientific community, myself included, had marshalled. It contained ambitious quantitative thresholds, such as those for the area of ecosystem to be protected, the percentage of genetic diversity to be maintained, and percentage reductions for overall extinction rates, pesticide use and subsidies harmful to biodiversity.

Then came the square brackets. In the world of policy, these mark proposed amendments that the parties do not yet agree on. The square brackets proliferated at an alarming rate throughout the GBF text, enclosing, neutralizing and paralysing goals and targets. By July 2021, in a version about 10,200 words long, there were more than 900 pairs of square brackets.

Brackets germinated with particular vigour in sections that could make the greatest difference for a better future because of their precision, ambition or conceptual novelty. Almost all quantitative thresholds had been bracketed or had disappeared.

I applaud the new prominence given to gender justice (with a new dedicated Target 22) and to financial resources and capacity building (Target 19). I wonder why other key aspects have not received the same treatment, and have instead been compressed almost beyond recognition. For example, the first draft highlighted that species, ecosystems, genetic diversity and nature’s contribution to people each needed their own specific, verifiable outcomes. Now they have coagulated into one vague yet verbose paragraph.

This thicket of square brackets smothers the GBF and the hopes of those of us who see transformative change as the only way forward for life on Earth as we know it.

In a titanic effort, a streamlined proposal from the Informal Group on the GBF has halved the brackets to be considered by the parties when they meet in Montreal, Canada, for the 15th Conference of the Parties (COP15) on 7–19 December.

We need a text with teeth — and far fewer brackets. This much we have learnt in the 30 years since the foundational 1992 Rio Summit drew attention to the impact of human activities on the environment: a strong, precise, ambitious text does not in itself ensure successful implementation, but a weak, vague, toothless text almost guarantees failure.

It was no surprise when the Convention on Biological Diversity officially declared the failure of its ten-year Aichi Targets. People involved at the international interface of biodiversity science and policy were already discussing how to do better in the next decade with the GBF.

The scientific community rose to the occasion. In just three years, we produced the first-ever intergovernmental appraisal of life on Earth and what it means to people: The Global Assessment Report on Biodiversity and Ecosystem Services from IPBES (the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services), which I co-chaired. It was ready in time for the original 2020 date for COP15, before the global disruption caused by COVID-19. It was the most comprehensive ever synthesis of published information on the topic, an inclusive conceptual framework involving various disciplines and knowledge systems, and unprecedented participation of Indigenous peoples.

Then, in 2020, we assembled an interdisciplinary team of more than 60 biodiversity scientists across the world, and within a few months produced detailed suggestions for the goals of the GBF. Since then, we have made the best of the many pandemic postponements by issuing a stream of specific, evidence-based recommendations on targets, scenarios and implementation.

The scientific advice is convergent. First, the GBF needs to explicitly address each facet of biodiversity; none is a good substitute or umbrella for the others. Second, the biodiversity goals must be more ambitious than ever, accompanied by equally ambitious targets for concrete action and sufficient resources to make them happen. Third, the targets need to be precise, traceable and coordinated.

Fourth, formally protecting a proportion of the planet’s most pristine ecosystems will by itself fall far short. Nature must be mainstreamed, incorporated in decisions made for the landscapes in which we live and work every day, well beyond protected areas. Finally, and most crucially, targets must focus on the root causes of biodiversity loss: the ways in which we consume, trade and allocate subsidies, incentives and safeguards.

From previous experience, I expected objections to certain sections— pesticides and subsidies, say — but they are everywhere. Only 2 of the 22 targets have no brackets. Ironing out objections takes precious time. Because the framework can be enshrined only by consensus, too many objections can lead to too much compromise.

Now, to avert failure, we exhort the governments gathering in Montreal to be brave, long-sighted and open-hearted, and to produce a visionary, ambitious biodiversity framework, grounded in knowledge. The awareness and mobilization of their constituencies has never been greater, the evidence in their hands never clearer. If not now, when?