This study demonstrates that ants and termites, the soil macrofauna in this dry and hot region, were associated with higher wheat crop yield under a low tillage, controlled traffic, but otherwise conventional agricultural management. We hypothesized two functional roles of the insects that could provide potential mechanisms to enhance yield, one of which was identified and a second was suggested in this study. The identified functional role was the digging of tunnels by the ants and the termites, which they do to forage and nest. These tunnels are a type of soil macropore26,27,28,29 that allowed more rain water to infiltrate into the soil. Greater water infiltration deeper into the soil leads to lower evaporation from the soil surface, allowing plants a better access to the available water. It is also possible that greater infiltration leads to lower water run-off and erosion35.

The second activity was the effect on mineral nitrogen by the insects in the soil. Although total mineral nitrogen declined overall, it did not decline as quickly in control compared with exclusion plots. In addition, as the yield was higher in the control plots, it seems likely that more nitrogen was removed from the soil by the wheat plants in these plots. If so, then the differences in mineral nitrogen in the soil between control and exclusion plots would have been greater than that measured. Although our understanding of the soil nitrogen cycle and how plants use soil nitrogen is developing36, there are several possible explanations for this effect: decreased mineralization, increased immobilization and increased denitrification. Another possibility is nitrogen fixation, normally associated with legumes37, but found in termites33,34, which has been implicated in native habitats38,39. We did not investigate all these possibilities, which can be influenced by abiotic or biotic factors36. We did, however, find evidence for nitrogen-fixing capacity by termites from the field. Whatever the exact mechanism, the presence of ants and the termites reduced the decline of total nitrogen by ∼9 mg kg−1 over the experiment, which corresponds to around 8 kg nitrogen per ha. This corresponds to 22–32% of the nitrogen typically added as urea fertilizer on farms in the region, suggesting that maintaining these soil macrofauna may help to lower fertilizer costs.

The effects we found are large, and perhaps could have been predicted from the large impacts ants and termites are known to have on soil and biotic communities in natural habitats. They move tonnes of soil per hectare, increase aeration and influence availability of several nutrients26,27,28,29,40. They have direct and indirect effects on plants and herbivores and even indirect effects on predators in natural systems41,42,43,44; hence, perhaps, it is not surprising that they had such a large impact in an agricultural system. Their impacts on natural ecosystems appear to be greatest in hot and seasonally dry climates25,26,27,28,29, similar to that of the area in which this experiment was conducted. Water is a limiting resource for plant growth in such conditions in non-irrigated agriculture45; therefore, it is under these conditions that the beneficial ecosystem services, especially water infiltration into the soil46, would be expected to result in an increase in crop yield. This phenomenon might explain why no-tillage fields have been reported to produce higher yields than conventional tillage fields in lower rainfall years in Mediterranean environments47. It may be that this phenomenon is less important in wetter habitats, because water is not as limiting to plant growth and therefore to crop yield.

Is it possible to capture the ecosystem service benefits created by ants and termites in agriculture in dry and hot climates, as has occurred for earthworms in wet and cool ones? There is evidence that traditional agriculture in tropical West Africa does already, as people place plant mulch and wood onto degraded soil to increase termite activity, and thereby improve the soil for cultivation48,49. Traditional agricultural knowledge is not well known outside their traditional cultures50, and scaling from 1-ha traditional farms to thousands of hectares in intensive agriculture may prove difficult. Lessons may be learnt from managing earthworms in agriculture; these mostly follow 'conservation agriculture' management for reducing erosion, such as reduced tillage, controlled traffic and reduced use of pesticides.

The farm on which the experiment was run uses some conservation agriculture management methods and has a diverse ant and termite community; therefore, it seems likely that these methods will prove beneficial to the soil macrofauna communities in other dry and hot climates as well. The shallow tillage used as mechanical weed control did not appear to affect the soil insects or their effect on crop yield, indicating that shallow tillage may be used without damaging soil fauna. This will increase environmental sustainability while increasing economic sustainability by reducing inputs and increasing yields2,7,8,9,10,11,12. Clearly, these low-impact management methods will benefit soil macrofauna already found on the farm. There remains the issue of how farms without ants and termites, due to decades of intensive tillage and pesticide application, can acquire them. This is a non-trivial issue, given the size of intensively managed farms, the sometimes very low portion of land with native vegetation communities and fragmentation of such habitat4,11,51, which even then can have degraded ant and termite communities52.

The results may become relevant in the future to areas predicted to become hotter and drier under climate change. Annual rainfall is predicted to decrease between 30 and 180 mm in subtropical and warm temperate latitudes, resulting in a decrease of up to 20% soil moisture53, especially with Mediterranean and savanna climates, and including areas used to grow cereal crops such as wheat31. Regions most likely to experience these changes include Northern Africa (Morocco to Egypt), Southern Africa (South Africa to Botswana), Southwest Asia (Turkey to Azerbaijan), Southern Australia, Southern Europe (Spain to Greece), Southwest North America (Panama to California) and southern South America (Chile)53,54. Future cereal production has many pressing issues, including erosion and nitrogen availability2,3,4,5,6,55,56, in addition to climate change; perhaps, capturing the ecosystem services provided by ants and termites will help reduce future unpredictability of food supply1,2,7,8,12,55,56.

Questions about specific details remain to be investigated. These include whether some species or functional groups were more important than others. Earthworms are grouped according to their foraging and ecology, which affects tunnel structure and thus water infiltration in soil. The highest water infiltration is in soil with endogeic (soil foraging and soil dwelling) species and anecic (surface foraging and soil dwelling) species; the lowest is with epigeic (surface foraging and surface dwelling) species13,14,57. Our exclusion results may suggest that insects with differing foraging patterns affect water infiltration differentially. The higher water infiltration in control plots may have been due to surface foraging ants (such as Melophorus, Meranoplus, Monomorium and Pheidole) and grass-harvesting termites (Amitermes and Drepanotermes) that live in the soil, creating an opening to the soil surface similar to anecic earthworms. In comparison, exclusion plots had some wood-feeding termites that were feeding in deeper soil on the roots of the felled trees and shrubs of the original native vegetation, as they were not affected by the insecticide. As these termites were foraging and dwelling deeper in the soil, their tunnels did not open to the soil surface, and hence correspond to the lower water infiltration. The nitrogen cycle remains to be investigated in detail, including the mechanisms of fixation, mineralization, immobilization and denitrification in the microbe community and in the micro-, meso- and macrofauna communities36. Such information is likely to lead to improved management for ecosystem services in dryland cropping.