Which environmental trend threatened the long-term productivity of pre-Columbian chinampa agricultural systems?

💡 Explanation

When over-pumping happened inland, the mechanism of brackish water intrusion was a risk because lowered water tables near coastal areas allowed saline water to flow upwards into irrigation ditches, especially along the valley base, poisoning croplands. Therefore brackish intrusion threatens chinampas rather than topsoil loss/methane release/microbe immobilization since these relate to other farming systems or require different failure pathways.

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