Early in the fourth century Constantine (r. 306–337) drastically changed the organizational structure of the Roman army. A usurper who had gained power through civil war, Constantine was most concerned with protecting himself from other would-be emperors. He created large, mobile field armies called comitatenses, commanded by himself and intended to protect his person and thwart attempts on the throne. As part of these security arrangements he and succeeding emperors abandoned Rome as a capital, moving often to avoid threats to their safety. This crippled the empire’s central administration, as slow communications and uncertainty at the court made it difficult for the bureaucracy to operate efficiently. This was especially detrimental for the army, which relied on state bureaucrats to provide the materials, manpower and finances for war.
On one of the piers, we find a collection of cracked-open crayfish shells, likely the remains of a heron’s feast. We paddle on, and a family of mallard ducks parts to let us pass, then rejoins behind us. Charlotte laughs and slaps the water with the paddle, getting Seamus wet. At the base of another pier, she picks some flowering chives to nibble on. Beyond those, a grove of tall grasses, reeds, and yellow flowers. By the end of the day, we’ll have seen blue herons, hawk-like ospreys, and two good-size beavers, which will scurry away as we approach but remain hidden in plain sight, one just below the river’s surface, its eyes and snout peeking out, the other lurking behind some more wood pilings, knocking soil and branches into the water.
Studying my then-and-now image pairs for signs of a changing climate, I find evidence of recent forest fires, loss of river flow, and natural and unnatural geomorphologic changes such as destruction of meanders and disappearance of sandbanks. I also see the growth of invasive and water-consumptive plant species like tamarisk and Russian olive, along with an incredible greening of river valleys that were barren in the 19th century. And there are many signs of the conceit of human engineering, from ditches to dams, transforming once pristine rivers throughout the southwest into sportsmen's paradises—in other words, reservoirs—frequented by loud motorboats, harboring the gasping Asian carp and invasive quagga mussels, and heavily stocked with sport fishes; and irrigation canals, contaminated with pesticides and agricultural runoff, that largely serve dairy cows (60 percent of the water used for irrigation, or about a third of the river, goes to grow hay and forage crops , according to the Pacific Institute).