The actual reasons behind the increase in asylum denials is not clear from the TRAC report. But increased resources, efforts by DOJ to speed removal cases, and a shift in focus from the prior administration to the present one likely had a significant effect.
There's no minimum age for spousal immigration, but the marriage is required to be "valid". Defining underage marriages as not valid for immigration purposes would end up in court, but it would be worth the fight even if DHS were to lose.
A recent article shows that the administration is correct about the reasons that foreign nationals are flooding to the border illegally, the incentives for them to do so, and the dangers that they face.
The nation's debates on environmental policies would benefit from the participation of a once well-respected conservation group like the Sierra Club and its deep bench of experts. But perhaps the club has determined there's simply more money in Bob Mueller and border walls than in biofuels and burning coal.
Considering furloughed IJs for detained cases is worth a shot
This would enable the now-furloughed judges to work during the shutdown; it would help to mitigate any increase in the backlog (and would likely reduce it in the long run); it would free up detention space; and it would serve the interests of justice by speeding up the asylum process for those who are detained, and who have applications pending.