There is a clear need for transformative change in the land management and food production sectors to address the global land challenges of climate change mitigation, climate change adaptation, combatting land degradation and desertification, and delivering food security (referred to hereafter as “land challenges”). We assess the potential for 40 practices to address these land challenges and find that: Nine options deliver medium to large benefits for all four land challenges. A further two options have no global estimates for adaptation, but have medium to large benefits for all other land challenges.

Five options have large mitigation potential (>3 Gt CO2eq/year) without adverse impacts on the other land challenges. Five options have moderate mitigation potential, with no adverse impacts on the other land challenges. Sixteen practices have large adaptation potential (>25 million people benefit), without adverse side effects on other land challenges. Most practices can be applied without competing for available land. However, seven options could result in competition for land. A large number of practices do not require dedicated land, including several land management options, all value chain options, and all risk management options. Four options could greatly increase competition for land if applied at a large scale, though the impact is scale and context specific, highlighting the need for safeguards to ensure that expansion of land for mitigation does not impact natural systems and food security.

A number of practices, such as increased food productivity, dietary change and reduced food loss and waste, can reduce demand for land conversion, thereby potentially freeing-up land and creating opportunities for enhanced implementation of other practices, making them important components of portfolios of practices to address the combined land challenges.

Many of the greatest current global challenges are related to the food system and the way that land is used and managed. Among the most pressing of these global challenges are the need to mitigate and adapt to climate change, the need to combat desertification and land degradation, and the need to deliver food security. These are collectively referred to, hereafter, as the “land challenges.” Given that many of the land challenges are related, there is a clear need to facilitate transformative change in land management and food production systems to address these global land challenges (Alexander, Rounsevell, Henry, Reddy, & Brown, 2019; Reed & Stringer, 2016; Webb et al., 2017).

A number of practices have been suggested to address one or more of these land challenges. The practices considered in this study can be categorized into those that rely on (a) land management; (b) value chain management; and (c) risk management (Figure 1). The land management practices can be grouped according to those that are applied in agriculture, in forests, on soils, in other/all ecosystems and those that are applied specifically for carbon dioxide removal (CDR). There is overlap in the categories; for example, the soil-based strategies can be applied in agricultural or forestry systems; feedstock production for bioenergy can be an agricultural or forestry activity. The value chain management practices can be categorized as those based on demand management and supply management. The risk management options are grouped together (Figure 1).
In this paper, we assess quantitatively at the global scale the potential of 40 practices (Figure 1, lower boxes) for addressing each of these land challenges (note that food security is largely addressed from an undernutrition perspective), in order to identify those that deliver across more than one challenge, and those that can result in trade-offs across the land challenges.
2 MATERIALS AND METHODS

Practices available to address the land challenges of climate change mitigation, climate change adaptation, land degradation, desertification, and food security were collated from the literature. These practices are described in Tables 1-3 for land management-based, value chain management-based, and risk management-based practices, respectively, with context caveats and supporting references provided in Tables S1–S3.




the full list of authors
Pete Smith, Katherine Calvin, Johnson Nkem, Donovan Campbell, Francesco Cherubini, Giacomo Grassi, Vladimir Korotkov, Anh Le Hoang, Shuaib Lwasa, Pamela McElwee, Ephraim Nkonya, Nobuko Saigusa, Jean-Francois Soussana, Miguel Angel Taboada, Frances C. Manning, Dorothy Nampanzira, Cristina Arias-Navarro, Matteo Vizzarri, Jo House, Stephanie Roe, Annette Cowie, Mark Rounsevell, Almut Arneth