Mobilising urban knowledge in an infodemic: Urban observatories, sustainable development and the COVID-19 crisis.

Along with disastrous health and economic implications, COVID-19 has also been an epidemic of misinformation and rumours - an 'infodemic'. The desire for robust, evidence-based policymaking in this time of disruption has been at the heart of the multilateral response to the crisis, not least in terms of supporting a continuing agenda for global sustainable development. The role of boundary-spanning knowledge institutions in this context could be pivotal, not least in cities, where much of the pandemic has struck. 'Urban observatories' have emerged as an example of such institutions; harbouring great potential to produce and share knowledge supporting sustainable and equitable processes of recovery. Building on four 'live' case studies during the crisis of institutions based in Johannesburg, Karachi, Freetown and Bangalore, our research note aims to capture the role of these institutions, and what it means to span knowledge boundaries in the current crisis. We do so with an eye towards a better understanding of their knowledge mobilisation practices in contributing towards sustainable urban development. We highlight that the crisis offers a key window for urban observatories to play a progressive and effective role for sustainable and inclusive development. However, we also underline continuing challenges in these boundary knowledge dynamics: including issues of institutional trust, inequality of voices, collective memory, and the balance between normative and advisory roles for observatories.

Rapid Removal of Atmospheric CO2 by Urban Soils.

The measured calcium carbonate content of soils to a depth of 100 mm at a large urban development site has increased over 18 months at a rate that corresponds to the sequestration of 85 t of CO2/ha (8.5 kg of CO2 m(-2)) annually. This is a consequence of rapid weathering of calcium silicate and hydroxide minerals derived from the demolition of concrete structures, which releases Ca that combines with CO2 ultimately derived from the atmosphere, precipitating as calcite. Stable isotope data confirm an atmospheric origin for carbonate carbon, and 14C dating indicates the predominance of modern carbon in the pedogenic calcite. Trial pits show that carbonation extends to depths of ≥1 m. Work at other sites shows that the occurrence of pedogenic carbonates is widespread in artificially created urban soils containing Ca and Mg silicate minerals. Appropriate management of fewer than 12000 ha of urban land to maximize calcite precipitation has the potential to remove 1 million t of CO2 from the atmosphere annually. The maximal global potential is estimated to be approximately 700-1200 Mt of CO2 per year (representing 2.0-3.7% of total emissions from fossil fuel combustion) based on current rates of production of industry-derived Ca- and Mg-bearing materials.