One of the greatest challenges facing the world today is population growth. How do we feed the ever increasing population with resources that seem finite? The earth holding an amount of resources too limited to feed a large population is a common Malthusian misconception. With better food practices, such as reducing food waste and managing agricultural lands more efficiently, a growing population can be sustained. However, a growing population will not be able to live comfortably alongside the dramatic effects of climate change, such as disruptions to growing seasons and the inability of crops to flourish in historically fertile areas. As a nature based climate solution (NCS), grasslands can help, not only by capturing carbon from the atmosphere, but assisting in the agricultural industry and the power of remote sensing can create a convenient system to monitor these grasslands.
A traditional practice is to convert grasslands to agricultural lands, however grasslands hold an astonishing ability to sequester atmospheric carbon deep into the soil, more effectively than croplands or forest. It is estimated that the amount of carbon in global soil stocks is about 3.3 times that which is in the atmosphere, posing a great threat to the already at risk climate scenario we are in if grasslands continue to become degraded croplands. When grasslands are converted into croplands, about half of the soil organic carbon (SOC) is lost to the atmosphere during tilling. When used as poorly managed rangelands, grasslands can become overgrazed leading to the infertility of the area and thus a reduction in SOC. These practices lead not only to an initial loss of SOC, but a continued decrease in ability for the area to accumulate SOC from the atmosphere. A result of this degradation can be desertification which leaves the land useless and barren, unable to sustain a herd, crops, or sequester carbon well. Grasslands hold more biomass than croplands as deep rooted perennial grasses pull carbon from the atmosphere and sequester it into the soil. A layer of mulch keeps dead plant matter from oxidizing (releasing CO2) into the atmosphere while in croplands, crop residue is left to decompose in the open, resulting in the release of CO2 into the atmosphere. Grasslands have some benefits over forests, for example their biomass is mostly underground. This prevents a great amount of carbon being released into the atmosphere during fires.
At this point, one may wonder how converting agricultural lands back into grasslands can actually help agriculture. As the world continues to develop, the demand for meat and dairy will rise due to the correlation of development and rising incomes. Properly managed grasslands can sustain livestock. Furthermore, the most productive agricultural lands would remain croplands for human consumption, while conversion to grassland would be focused on the abundant degraded croplands whose production is not sustainable. Techniques such as reduced grazing intensity, the application of nitrogen fertilizers, proper irrigation, and the introduction of diverse species of long rooted grasses would increase the ability of grasslands to capture SOC and create sustainable rangelands to meet the food demands of the world.
As calls to action surrounding climate change are increasingly responded to, a successful carbon market is likely to arise. This could include a cap-and-trade system or incentives for farmers to capture more SOC in their land. Systems that reward landowners for the amount of SOC stored in their land are most applicable to the NCS consisting of converting degraded croplands to grasslands. In the monitoring, reporting, and verification (MRV) of converted grasslands, remote sensing holds promise. The permanence and effectiveness of these grasslands can be monitored using vegetation indexes, such as NDVI, which show the amount of healthy vegetation in an area and, as grassland vegetation is known to sequester carbon, it hints at the success of grasslands in holding SOC. SOC can also be monitored directly using VNIR and SWIR which reveal soil properties that indicate the SOC content. These measurements derived from satellite imagery can provide a quick and cheap method to monitor grassland conversion projects by detecting change over time in vegetation and soil, allowing decision makers to create fluid management practices to improve ongoing efforts as well as to consistently and accurately compensate landowners for SOC.
Since the beginning of industrialism, agriculture accounts for about 20% of global greenhouse gases released. Converting croplands into grasslands would not only work towards sustainability in a historically unsustainable industry, but continue to allow for food production to support the world’s large population. Remote sensing can uplift the feasibility of global cropland to grassland conversion projects, by creating a monitoring system that is efficient, cost effective, and accurate.