Agriculture and other aspects of global change can alter the capacity of soils to store organic carbon and to resist erosion. Mycorrhizal fungi can also mediate soil responses to global change, and in doing so they may offset or accentuate carbon sequestration and erosion. For instance, arbuscular mycorrhizal fungi are the only organisms known to produce glomalin, a glycoprotein that can reside in the soil for years to decades. Because it has a long residence time, glomalin accumulates until it represents as much as 5% of soil carbon. As such, glomalin may sequester a large amount of carbon globally. In addition, glomalin appears to increase soil aggregation, which deters erosion. Nevertheless, examinations of environmental controls over glomalin are still in their early stages.

Arbuscular mycorrhizal fungi rely almost completely on their host plants as a source of carbon. Therefore, environmental conditions that influence the carbon status of plants can also influence arbuscular mycorrhizal fungi. One example is atmospheric CO₂ enrichment, which increases photosynthetic rates in plants and accentuates nitrogen or phosphorus limitation of plant growth. In response, plants appear to allocate a greater proportion of photosynthate to mycorrhizal fungi to improve nutrient acquisition. Elevated CO₂ often is accompanied by an increase in abundance of arbuscular mycorrhizal fungi. Concentrations of soil glomalin are likewise enhanced. In contrast, anthropogenic nitrogen deposition has the opposite effect on arbuscular mycorrhizal fungi and glomalin, most likely because plants allocate fewer resources to their fungal symbionts when soil nutrients are less limiting. Globally, soil glomalin stocks increase linearly with precipitation across ecosystems; water relations of the fungi or the plants may be another important consideration. By examining the ecology of mycorrhizal fungi and their relations with host plants, we may better predict and manipulate soil conditions under various elements of global change.