This study investigates the presence of an energy and environmental rebound effect from the adoption of autonomous vehicle (AV) ride-sharing technologies. We take an adoption pattern and market share competition framework to show how environmental gains from increased fuel efficiency and favorable travel attributes of AVs may be offset by unintended modal shifts. The analysis is informed by a revealed and stated preference (RP/SP) travel survey data collected in Chicago, Illinois. Our results show that while AV ride-sharing reduces emissions when replacing personal vehicles, it frequently substitutes energy-efficient modes such as walking and biking, thereby undermining these gains. Specifically, we show that substituting a one-mile walking trip with an AV ride-sharing trip requires the displacement of up to six miles of personal vehicle travel to offset the resulting emissions. This non-linearity in magnitude of substitution works against AV technologies in the current competition between traditional, public, and micro-mobility options. The study reveals a systematic environmental rebound effect with important implications for the next-era transportation systems. All codes used in this study are made available in the attached Supplementary Information.