Ecohydrology Controls the Geomorphic Response to Climate Change

Erosion rate data worldwide show complex and contrasting dependencies to climate. Laboratory and numerical model experiments on abiotic landscapes suggest a positive response: Wetter (drier) shift in climate leads to an increase (decrease) in erosion rates with longer relaxation times under a drier climate. We performed eco‐geomorphic landscape evolution model simulations driven by abrupt climate shift in a semiarid climate. With dynamic vegetation, the erosional response to climate shift was opposite to bare soil, variability of erosion rate lessened, and landscape relaxation time scales became insensitive to climate change direction. The spatial geomorphic response to a wetter climate was depositional in vegetated, incisional in barren landscapes, and got reversed with drier climate. A relationship between net erosion rate and mean landscape slope emerged, exhibiting a hysteresis loop. Our study offers insights to the interpretation of observed acceleration of erosion rates and increase mountain relief during Quaternary climate change. Plain Language Summary In semiarid ecosystems, the plant growth is limited by available soil moisture. Therefore, wet years cause denser vegetation than dry years. When there is no vegetation on the ground, soil is prone to erosion; therefore, wet climate causes more erosion than dry climate. However, when the surface is protected by vegetation against erosion, two counteracting factors compete for erosion: more erosive power due to enhanced precipitation and more erosion protection by vegetation due to more vegetation. These counteracting forces shape the landscape in real world. Here we show with a numerical model how a climate shift from dry‐to‐wet may result in less erosion in vegetated landscapes. The reverse case may happen in wet‐to‐dry climate shift. However, over the long‐time frame of landscape response, uplift‐erosion equilibrium is attained in both cases. Key Points Vegetation exerts a major control on equilibrium slopes, erosion rates, and response times to climate shifts Vegetated and unvegetated landscapes could show contrasting response patterns to climate change The interpretations of erosional records of past climates need to account for the effect of coevolving vegetation