Remote environmental surveillance by massively deployed tiny wireless sensors requires energy efficient communication and network protocols so as to prolong the network lifetime. A load-balanced cluster-based cooperative MIMO (multiple-in-multiple-out) transmission scheme for such wireless sensor networks is proposed, taking imperfect data aggregation into consideration. In this scheme, a two-layer hierarchy is formed by clustering, and the cluster heads perform local data aggregation, balance communication loads and transmit data back to the base station using cooperative MIMO techniques. Simulation results show that the proposed scheme can distribute the energy dissipation more evenly throughout the network and achieve higher energy efficiency, which leads to a longer network life span compared with other traditional schemes.