If we think in terms of decadal time scales, then the world is approaching a critical inflection point for climate action. The 1990s saw the dawning of global awareness about climate change and the first international policies aimed at addressing it. And the world has now committed to reduce annual net emissions to zero by the 2050s, in order to avoid the most harmful and disruptive impacts of climate change. Thus, we are now approaching the midpoint of a 60-year arc of history during which the world must eliminate its greenhouse gas pollution. The land sector has a critical role to play in this process, since it currently removes nearly 10 gigatons of carbon dioxide (CO₂) from the atmosphere every year—about one-fifth of our global annual emissions—through photosynthesis (Smith et al. 2014). To bring greenhouse gases into a global balance between emissions and removals, we likely will need to roughly double the annual sequestration in the land sector, while virtually eliminating emissions from land clearing (Rockström et al. 2017). The long-term climate strategies that the Paris Agreement invites from countries could be a key tool in coordinating such a sustained and transformative effort. In preparation for developing such strategies, this essay addresses the question of what it would take to achieve these conditions over the next three decades.

History shows that humanity does not have a good track record when it comes to maintaining and restoring the ecosystems that sequester carbon. In fact, our record in postindustrial times has been just the opposite: we have accelerated our ability to clear forests, destroy wetlands, and plow carbon-rich soils. The forests we have left today—about 4 billion hectares—are likely only about two-thirds as extensive as forests in preindustrial times (FAO 2012; Williams 2003). We have also lost as much as one-third of global wetlands (Hu et al. 2017), and agricultural soils have probably lost about 116 petagrams (billion metric tons) of carbon (Sanderman et al. 2017).

The few examples we have of large-scale reforestation in recent decades have often been driven by circumstances ranging from the tragic to the painfully destructive. For instance, the northeastern United States has become largely reforested in the last century due to the widespread abandonment of farming in the region and the failure of rural economies (Forster et al. 2010). A similar process occurred more abruptly and more recently across Eastern Europe after the fall of the Soviet Union, which may have led to as much as 100 million hectares of new forest area (Potapov et al. 2014). And in South Korea, Western Europe, and Vietnam, the restoration of forests has occurred during the recovery from devastating wars that ravaged landscapes and shattered societies. No one—especially politicians—sees any appeal in replicating these circumstances for the sake of saving the climate.

Even so, these destructive examples may hold clues about how to achieve widespread ecosystem restoration in a sustainable way that improves livelihoods instead of damaging them. Clearly, there is an economic dimension to these changes. For example, when agricultural subsidies stopped flowing from the Soviet Union, vast areas dedicated to agriculture were no longer profitable, and they reverted to forests over subsequent decades (Potapov et al. 2014). A similar economic story played out over a century in the northeastern United States, where the relatively unproductive soils of the region simply could not compete against other regions with more fertile soils, cheaper labor, or greater ability to take advantage of efficiencies delivered by mechanization and scale (Forster et al. 2010). Modern farming seems to be an arms race between increasing efficiency and narrowing profit margins: the result is that farming is a lucrative prospect for very few of its practitioners; for most others, it is a marginal enterprise.

This feature of land economics suggests that relatively small incentives could potentially tip the balance of land use in the other direction, when done carefully. Programs like the Conservation Reserve Program in the United States and the Payments for Environmental Services (PES) program in Costa Rica have shown that relatively small incentives can achieve outsized impacts on land-use decisions, under the right design conditions (Börner et al. 2017). Over time, land managers have utilized these programs to make their own operations more efficient by focusing their production activities on the most profitable areas. These programs introduced a new factor into the landscape, causing land managers to sort land into more efficient uses, based not only on its profitability for production but also on the value of the environmental services it can provide. This is the dynamic we must replicate on a global scale if we are going to reach our climate goals.

Successful examples make the prospect of shifting global land-use patterns over the next 30 years seem a little less daunting, albeit still ambitious. Recent science and land-use modeling are starting to point the way. Spatial economic analysis is a tool that can highlight the specific areas that would be more likely to change land use under a given set of incentives, illuminating the locations and degrees of change across landscapes (e.g., Funk et al. 2014). At the global scale, recent analyses suggest that modest incentives for reducing emissions and increasing carbon sequestration—on the order of US$10 per ton of CO₂-equivalent—could trigger about half of the shift in emissions we need to double the land sector sink (about 4 billion tons CO₂-equivalent annually; Griscom et al. 2017). We have some sense of the volume of emissions reductions and/or carbon sequestration available in different regions or countries (see supplement to Griscom et al. 2017), but we do not yet have the kind of detailed, spatially explicit, and globally consistent analysis available that would tell us what to expect from a global rollout of carbon incentives. This is an important near-term priority for research—one that could also inform countries’ long-term strategies.

The global consistency of such analyses is important because incentives themselves must be applied consistently across the wide variety of global contexts; otherwise, any gains in one region could “leak” away through losses elsewhere. “Leakage” occurs when the benefits of policy-driven changes in land use in one country or jurisdiction are accompanied by detrimental changes elsewhere, driven by those same policies. This effect has already been observed in the United States, where policies aimed at replacing fossil fuels with biofuels had the unintended effect of triggering an expansion of agricultural production, ultimately increasing greenhouse gas emissions (Lark et al. 2015). Such examples highlight the importance of coordination in policy implementation, with a holistic view of how policies might have impacts across sectors and jurisdictions.

The prospect of leakage, within and across sectors, becomes much more important as we contemplate the deep decarbonization of our economic systems. Integrated assessment models are tools that have been developed specifically to address these issues, and some of the earliest results of these models highlighted the sensitivity of the land sector to policy incentives applied elsewhere. Such models have consistently predicted that climate policies would, paradoxically, trigger massive losses of forest ecosystems when they exclude the land sector from climate mitigation efforts (Wise et al. 2009; Reilly et al. 2012). Often these modeled scenarios involve widespread conversion of forests to bioenergy crops.

Given the enormous risks associated with straying off course and our spotty record of past success, how will we navigate a path for the land sector that can achieve our goals, while withstanding the stormy economic seas ahead? Specifically, what objectives should guide countries, individually and collectively, in designing a long-term vision and implementing supporting actions? In my view, any successful path will need to follow five key principles:

1. Ubiquity: Policies (incentives and disincentives) apply to all geographic areas of all countries, to prevent the possibility of leakage.
2. Parity: Policies must create equivalent incentives (or disincentives) for each unit of mitigation (or emissions), regardless of sector or location.
3. Stability: Policies must be structured to deliver durable, long-term incentives (and disincentives), as they do in PES programs, facilitating near-term changes in land use.
4. Accessibility: Policies must be supported by means of implementation, so that decisions about mitigation activities are not penalized by a lack of capacity or the lack of access to information.
5. Consistency: Policies to incentivize progress must treat each measured unit of mitigation outcomes in terms of a standardized contribution to net reductions, consistent across national contexts.

Achieving these principles is key to the equitable achievement of the Paris goals and the sustained political will necessary to maintain a multidecade global effort. Fortunately, the adoption of the Paris Agreement in 2015 may have delivered the tools needed to achieve them. The agreement is broad enough to encompass and engage all countries, creating the opportunity for the ubiquitous application of policies. Each country will be at a different starting point when the Paris Agreement begins to be implemented in 2020, so progress toward the first guidepost will depend upon how quickly the nationally determined contributions (NDCs) of all countries can be expanded to fully cover their geographic areas—or at least the ecosystems that are most important from a climate perspective. The development of national long-term strategies should then become the basis for countries to coordinate their actions toward the achievement of the five principles, aiming for global convergence and coverage by 2050.

Toward this end, the Paris Agreement also made significant advances toward the “parity” and “consistency” guideposts. It created the expectation that all countries will move toward economy-wide climate commitments. And while NDCs initially started with widely different approaches, the Paris process has subsequently created basic expectations about how progress will be measured in standardized ways (the Paris “Rulebook”). It also established evaluative processes to assess progress at the global and national levels, and these assessments are likely to nudge countries toward more standardized and comprehensive approaches over time. Success on these fronts, again, will depend upon the pace of these distinct processes and the willingness of countries to coordinate their efforts.

The Paris Agreement also contains provisions that could support greater accessibility in the implementation of land sector mitigation. Specific sections of the agreement are dedicated to expanding the flows of capacity, technology, and finance to the countries that need them most. Furthermore, the overall ambition of the agreement means that countries are not likely to benefit from sitting on the sidelines, hoping to steal markets away from others that work aggressively to decarbonize their economies. As geographic coverage expands and countries work their way through the lowest-cost mitigation options, pressure will increase on the laggards to take action, while early movers may find themselves reaping a comparative advantage in a transformed global economy. With a little bit of luck, this could lead to countries “crowding in” on successful approaches.

Stability of long-term incentives is perhaps the place where the least progress was made in Paris—though careful scrutiny of the agreement suggests some hopeful features, sometimes hidden between the lines of the text itself. For instance, the agreement was designed to be more durable than its predecessor, the Kyoto Protocol, potentially lasting through 2050 with few changes in its fundamental terms. The agreement also builds upon and expands the role of international cooperative mechanisms, which can encourage harmonization, efficiency, and stability. The track record of such cooperative mechanisms has been mixed, and it requires a stretch of the imagination to envision a world in which incentives are delivered robustly and consistently everywhere, but such a vision can be credibly contemplated within the Paris framework. The stable, predictable delivery of incentives across all the relevant contexts will be key to achieving equity in its benefits, sustaining the political will for action, and attaining the overall success of the Paris Agreement. This aspect must be reinforced by progress toward each of the other principles: their mutually reinforcing nature could create the conditions for accelerating progress toward the Paris midcentury goals.

The land sector should be at the forefront of this acceleration, due to its potential to deliver substantial climate mitigation benefits at relatively low cost and to deliver other kinds of benefits. Decision-makers at all scales would be wise to select and promote activities that also enhance attainment of other Sustainable Development Goals, including climate resilience, protecting biodiversity, and boosting rural livelihoods, which can stretch the value of mitigation investments. The delivery of such benefits to on-the-ground stakeholders might be the single most important factor in creating the long-term political will necessary to sustain a commitment to achieving the Paris goals—and activities in the land sector may be the most direct channel for providing these benefits. As we look ahead to our long-term strategies for 2050, our first priorities must include planning, implementing, and sustaining early and thoughtful action in the land sector, guided by the five key principles for success.

References

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