We couldn’t agree more that analytical rigor is needed in comparing among land management options and global land systems for the benefit of biodiversity and a sustainable future for humanity. However, Blomqvist’s description of our article has rather unfortunately taken a number of things out of context, and we appreciate the opportunity to clarify a number of points.
First, this invited review from Science is part of their “Tomorrow’s Earth” series, and for it, we were asked to provide an aspirational perspective on what the Earth could look like in the future. We chose to portray a vision of Future Earth that we feel is both feasible and highly desirable, based on a large body of evidence (106 carefully-selected references were included in the Science article). The review shows how “working lands conservation” can complement protected area networks, which alone are not preventing the 6th mass extinction. Working lands are farmlands, forest lands, and rangelands that are managed for the production of natural resources. Working lands conservation, as we define it, requires using management techniques that maintain rather than degrade ecosystem services, and support the species that provide these services (“biodiversity-based management techniques”). It further promotes biodiversity in general (not just ecosystem service providing species) by creating a more inhabitable and permeable matrix. This is no manifesto, but rather a synopsis of a huge volume of literature documenting the importance of working landscapes for biodiversity conservation, and an acknowledgement of the progress that local community-led efforts have made as a hopeful direction for broader impacts for policy, sustainability, and the survival of future earth.
Second, our purpose was not to compare land-sharing with land-sparing, but instead, to show how necessary it is for biodiversity conservation to advance working lands conservation along with expanding protected areas. We agree with Blomqvist that trade-offs exist for any land management practice, and in fact included a conceptual figure to visualize “likely trade-offs and sustainability within and across patches (Fig. 2).” Our purely conceptual Figure 2 was not meant, nor did it claim, to be based on empirical data. It is similar to other diagrams produced in earlier papers that recognize the well-documented fact that highly-simplified, chemically-intensive agriculture, while generally highly productive, often simultaneously causes serious environmental impacts (Fig. 2A). Our diagram shows that when different land uses within a landscape are each sustainably managed to produce different goods and services, they can collectively provide a multi-functional basket of goods and services (Fig. 2C). The diagram focuses on working lands (comparing, for example, an area of monoculture against an equivalent area of managed forests, farms, and rangelands) without including protected areas. We did not diagram a potential larger-scale effect of nature-sparing that hypothetically might occur due to agricultural intensification, since our focus was not on the sparing-sharing debate.
Briefly, this debate oversimplifies many important ecological as well as socio-economic issues. First, density-yield studies of the type recommended by Green and Balmford and by Blomqvist in his article don’t assess the long-term consequences of isolating species in protected areas surrounded by inhospitable matrices, but substantial empirical data and models show that even very large protected areas will lose species if they remain isolated over time. Second, whether nature-sparing actually occurs in response to agricultural intensification is determined by markets, policies, and trade. In fact, agricultural intensification may paradoxically lead to greater amounts of habitat conversion rather than incentivizing additional protected land. For example, a recent global analysis shows that from 2001 to 2015, large-scale commodity crops were responsible for 64 ± 8% and 61 ± 13%, respectively, of deforestation in biodiverse Latin America and Asia, dwarfing other forms of forest disturbance, and leading to global, permanent losses of 5 million ha/yr. (However, in Africa, small-scale shifting agriculture was the dominant driver of forest cover loss at 93 ± 3%.) These observations of actual deforestation drivers do not suggest that intensified agriculture has had any nature-sparing effect in recent years.
Blomqvist’s key concern with our review is whether biodiversity-based management systems can be as productive as conventional, simplified, and chemically-intensive systems. We provide evidence for similar or superior productivity of many biodiversity-based farming systems (see main text and Supplementary Table 2), such as the push-pull system for maize production in Africa and intensive silvopastoral management systems for livestock production. Further, a wide array of agroforestry, water-harvesting, integrated crop-livestock, and other systems have been shown in several analyses to enhance production for smallholders that currently use subsistence or conventional methods by 79% – 116% on average. Smallholders with less than 5 ha make up 94% of the world’s 570 million farmers, and adopting such practices more widely, therefore, could increase their contribution to food production substantially, while enhancing their livelihoods and social equity generally. Since it is thought that only 50% of smallholders currently use such practices, our back-of-the-envelope calculation suggests that adoption by all smallholders could increase global production by 10 – 20%. Finally, such systems often demonstrate marked resilience to droughts, deluges, and hurricanes, making them “climate-smart” adaptations for farmers subject to the vagaries of a changing climate.
From a biodiversity perspective, farming systems that add structural vegetative diversity and complexity back into homogenous monocultures are likely to be most helpful. Silvopastoral systems, for example, in which forage grasses are planted along with nitrogen-fixing forage shrubs and shade-providing mixtures of fruit and native trees, provide a multi-layered system that enhance several biodiversity indicators (by 1.3 – 3 fold for ant and bird species richness, respectively), while simultaneously permitting greater meat or milk production per animal at higher stocking rates, compared to grass-only monocultures. Ultimately, the amount of land required per tonne of meat production annually was reduced by 92%, and the amount of methane (one of the most potent greenhouse gases) emitted per tonne was reduced by 42%. This silvopastoral system enhances profitability per animal, both because it is more productive and uses fewer costly fertilizers and pesticides, while being more beneficial for biodiversity and regenerating rather than destroying ecosystem services, including carbon sequestration and water storage. Importantly, since it actually uses less land per production unit, it incorporates aspects of both ‘sparing’ and ‘sharing.’
Some sensitive species will not inhabit the ‘novel’ ecosystem of a silvopastoral system, and thus these and other working lands should be seen as complements rather than replacements for protected areas. However, even sensitive species may be able to move through wooded or shrubby habitats more readily than through simplified agroecosystems. In our paper, we suggest that such multi-layered systems may enhance the permeability of the matrix landscapes and thus serve to interconnect and enhance the effectiveness of protected areas. Magical thinking — no — but magical solutions — yes — provides wins for the producer, the biodiversity, and the planet. Silvopastoral systems are starting to spread in Latin America and contribute to landscape-level connectivity, and even gain toe-holds in the United States (see the new book Wildly Successful Farming, by Brian Devore).
Not all systems provide win-win solutions, but even when displaying some trade-offs, very promising innovations exist that should be scaled up. In the US Midwest, some farmers are taking 10% of their land out of production to plant strips of native prairie. This action results in doubling the richness of bird and pollinator species while reducing runoff by 37%, leading to retention of 20 times more soil and 4.3 times more phosphorus, critical in a region plagued with severe water quality issues. Here, yields of corn and soy were reduced only by the amount of land taken out of production. Interestingly, Blomqvist suggests that farmland measures, with a sole focus on organic production, will only assist common generalist species; however, in this example — in one of the most-intensively farmed industrial farmscapes on Earth — the abundance of bird species of greatest concern also doubled. Precision agriculture may help make taking land out of production more palatable to the farmer by identifying specific areas less suitable for crop production. Taking such lands out of production and restoring prairie or other useful plants may allow large-scale farmers to maintain the same profits, or even cut losses during years of drought or deluge.
Blomqvist focused much of his concerns on organic agriculture, and while this farming system was not the focus of our paper, we did reference the trade-off between yield and sustainability for organic agriculture. Supporting our point about the important role of diversification in farming systems, a recent analysis showed that the organic-conventional yield gap can be more than halved simply by incorporating diversification measures such as intercropping or more complex crop rotations. Organic agriculture improves some, but not all, sustainability metrics, as Blomqvist points out. However, closing the yield gap further might allow it to provide greater sustainability on more dimensions, and might be possible through further research investment. For example, since most seeds available on the market today are bred for conventional farming systems and do poorly when grown in organic farming systems, cultivating seeds adapted to an organic farming environment could improve yields.
Blomqvist states that “if only agriculture can be intensified to spare more large blocks of habitat,” protected areas “could be expanded to such a degree that they would form a much more effective means of protecting biodiversity than they do today.” On first glance, this perspective appears to fit with E.O. Wilson’s proposal to “protect half the Earth to preserve 85% of the species.” However, a recent study hits home how important it is to consider both protected areas and complementary working landscapes, as opposed to simply grabbing the largest remaining wilderness areas. Pimm and colleagues showed that the only way to include 85% of the species in protected areas is to focus on regions of high species endemism, many of which, like the Atlantic rain forest of Brazil, are already highly fragmented. In such landscapes, the way to ensure species longevity is not only to protect but also to reconnect these habitats, and making working lands more permeable for species movement, in combination with restoration of critical linkages, could do exactly that.
A significant section of our paper references some of the more promising tools that can advance working lands conservation on private and public lands (see Supplemental Table 1), including indigenously-managed protected areas. There are many difficulties in advancing these tools because, for decades, the predominant model has been to simplify and intensify landscapes in the pursuit of economic gain. This has not served biodiversity well. Even common, widespread vertebrate species are now declining and insect biomass has declined by 76% within protected areas, likely due to the combined impacts of climate change and agricultural intensification. Unless we can enhance the protective qualities of surrounding landscapes, and create a more sustainable human enterprise, biodiversity will continue to be imperiled globally, even in parks.