## 7 Evolving Sensor Modalities  
The technologies developed for sensors to measure the temporal and spatial scales of our physical environment are generally more mature and robust in design than the existing technologies for chemical or biological sensors. A large commercial base exists for the design and manufacture of diverse modes of sensors for temperature, pressure, and physical properties (Table 1). Expanding on these existing commercial sensors, there is a need for modular sensor arrays and data loggers to provide three-dimensional parametric data for air, water, soil, and groundwater over spatial scales ranging from the micro (e.g., pore volume) to the mega (e.g., kilometer scale volumes). Innovative new imaging techniques for physical parameters are now available to assist in mapping the biogeochemical fluxes in spatial volumes at diverse scales. Multiple devices are now available to map atmospheric turbulence using 3D flow measurements at fine scales of a few cm.  
There is a clear need for an innovative development of chemical sensors for use in a variety of natural and anthropogenic environments (e.g., atmospheric, terrestrial (soils and sediments), and aquatic (groundwater, fresh and marine waters). Many existing chemical sensors are not robust enough to measure the key or fundamental chemical compounds and ions in sustained operations at high acquisition rates. Moreover, there is a need for greater precision and sensitivity to expand flux measurements at dynamic spatial and temporal scales (Table 1). Many electrochemical and optical oxygen sensors are known to be prone to biofouling for short periods of time. Biological sensors would be useful to measure diverse biological reactions. Oxygen, basic nutrients, hydrogen sulfide, pH, CO\({}_{2}\), NOx, NOx, CH\({}_{4}\), CO, O\({}_{3}\), Fe, Mn, and trace metals all may have significance in the ecosystem studies of biogeochemical fluxes and dynamics. As with the other types of sensors, the signals produced by biological sensors need to be processed in ways that allow for adaptive sensing. Furthermore, the sensors need to be capable of long-term deployment, and should be capable of integration with other sensing devices.  
There is great promise in the future development and installation of new sensor networks to involve new sensor modalities and expand traditional sensors for microclimate (Table 1). These include imagers and acoustic monitoring devices as sensors for detecting motion, vocalization, and other organismal activities and behaviors. There are, nevertheless, numerous challenges in designing and deploying successful ecological sensor networks. Some of these issues relate to science-driven questions and requirements that are specific to terrestrial, soil, or aquatic domains. In an observatory mode of operation, the goal is to provide a more complete \"fingerprint\" of ecosystem structure and function over time and space.  
Micrometeorologists have been measuring the CO\({}_{2}\) and water vapor exchange between vegetation and the atmosphere since the late 1950s and early 1960s. However, the routine application of the eddy covariance methodologies and associated data management that allowed for continuous flux measurements did not occur until the 1980s. Technological advances were made at this time in sonic anemometry, infrared spectrometry, and digital computation. Further technological developments over the past several decades have facilitated a larger data storage capacity, and the improved stability and precision in instruments have enabled scientists to build on pioneering ecosystem flux studies. Today, AI (artificial intelligence) is opening the door to new ways of monitoring the pulse of our environment and addressing the issues of global change.