BuddyPress.org

It isn’t possible by default. You would need to link an xProfile field with the author description.

Try this. Note that I’ve used field ID 1 on the 2nd line. You’ll need to change this to the ID of your xProfile field.

function deanljbirch_save_author_bio( $data ) {
    if ( 1 == $data->field_id ) {
        wp_update_user(
            array(
                'ID' => $data->user_id,
                'description' => $data->value
            )
        );
    }
}
add_action( 'xprofile_data_after_save', 'deanljbirch_save_author_bio' );

If a member updates the xProfile field, their author bio will be updated. Note that updates to the author bio won’t be synchronised with the xProfile field.