Mexico's president reacts to pressure from Leonardo DiCaprio to save a species.

On May 10, 2017, actor and activist Leonardo DiCaprio took to Twitter to save a marine species.

"The vaquita is the most endangered marine mammal in the world," he wrote of the species, which can only be found off Mexico's shores in the Gulf of California. "Join me [and the World Wildlife Fund] and take action."

It may seem like an average tweet, coming from one of the biggest environmental advocates in the world. But the tweet has had global ramifications.

As DiCaprio noted in a Facebook post that same day, unsustainable fishing has caused a steep decline in the total number of vaquitas.

There may only be 30 left in the gulf right now — a 90% drop since 2011 — which also explains why there seem to be so few photos of the rare porpoise in the wild.

One major reason for the falling numbers is China's hunger for the totoaba fish, which also only lives in the Gulf of California. Mexican fishermen use massive gill nets to catch the totoaba and ship the marine animals to China — an illegal practice in itself. But all too often, vaquitas get caught in these nets and are needlessly killed.

This doesn't just affect the vaquita either. Illegal fishing is harming many other marine species in the region, too — species that local communities rely on for food and business.

DiCaprio linked to a petition by the World Wildlife Fund calling on Mexican President Enrique Peña Nieto to act now to save the species in his Facebook post and tweet.

Among other demands, the letter urges the president to implement and enforce a permanent gill net fishing ban.

To Nieto's credit, his government has taken some steps to save the vaquita.

In 2015, Mexico implemented a two-year gill net fishing ban. But it wasn't properly enforced, advocates argued, which helps to explain why vaquita numbers continued to dwindle. What's more, what little effect the ban did have on dissuading fisherman is now gone entirely because the ban expired in April 2017.

DiCaprio's posts did actually catch the attention of the Mexican president, who responded on Twitter.

In a series of tweets, Nieto explained how his government has upped efforts to save the vaquita in recent years, such as expanding its protection zone in the gulf and committing 300 marines and 15 boats to monitor the area.

Still, DiCaprio's call to act seemed to spark new urgency from the Mexican president, who made a very public commitment to ensure the vaquita won't be lost forever.

Not everyone has over 17 million Twitter followers like DiCaprio, but we all have a voice.

Use it to tweet your support for the Word Wildlife Fund's petition and put more pressure on Nieto and Mexico to save the vaquita.