MORE than two million years ago, mammoths and Asian elephants took different evolutionary paths — and around the same time, according to DNA research, so did their lumbering relatives in Africa. African elephants have long been thought of as a single species, but a critical mass of genetic studies now proves there are two.

You can tell the species — “forest” elephants and “savanna” elephants — are different just by looking at them carefully, but until 2010 the jury was still out on the genetic evidence. Forest elephants are much smaller, weighing half what savanna elephants weigh, and evolved in Central and West Africa’s rain forests; they have rounder ears than their cousins and straighter tusks. Savanna elephants, whose ears are more triangular and whose tusks are thick and curved, roam throughout the open, bushy terrain of other parts of the vast continent, from East Africa down to the south, where they’re most abundant. The two species are about as distinct from each other, in genetic terms, as lions are from tigers.

Over the past decade a strong scientific consensus on the elephants’ biology has emerged. So, in June, the Center for Biological Diversity, where I work, filed a petition with the United States Fish and Wildlife Service to reclassify African elephants as two separate species and protect them both as “endangered” under the federal Endangered Species Act.

It may seem odd that the United States gives any legal status at all to animals in other countries, but the truth is that American protection of “foreign” animals or plants under the powerful Endangered Species Act can bring tangible benefits to those species, including preventing the animals’ parts from being sold in the United States and preventing our government from sanctioning or paying for actions that hurt the animals. It can also provide funds for research and public education.

The question of one versus two species of African elephants isn’t about settling an arcane DNA argument; it’s about life or death for these majestic, extraordinary creatures. Without elephants, Africa’s landscape would be unrecognizable, yet these animals have fallen by the hundreds of thousands as a result of two enormous waves of poaching in this century — one in the 1970s and 1980s, the other, beginning around 2009, now underway. If the center’s petition is granted, it could be a lifeline.

Here’s how. Right now, the two elephant species are treated as one and protected under the Endangered Species Act only as “threatened” — a less protective status than “endangered.” What “endangered” means for elephants, or any other animals or plants, is simple: There aren’t many left, so the species is at risk of going extinct. Acknowledging the scientific fact that these are two different animals reveals the truly low numbers — relative to historic abundance — of each one. Instead of looking at about half a million individuals remaining in a species, we’re likely looking at a maximum of 100,000 (and possibly as few as 50,000) forest elephants surviving in the world and an estimated 400,000 savanna elephants. It’s important to understand, though, that the actual figures could be much lower, since elephants are notoriously hard to count.

Populations of both species are in free fall as poaching frenzies drive the brutal killing and butchering, for their tusks, of tens of thousands of elephants every year. The number of Central African forest elephants declined by 62 percent in less than a decade, devastated by a lethal cocktail of illegal hunting, habitat loss and civil strife, and are the more urgently at risk of the two. Savanna elephant populations have also significantly declined throughout their range, with particular devastation in Tanzania, where one of the strongest populations of elephants — 109,000 animals — dropped to about 43,000 in just five years, between 2009 and 2014.

If the United States recognizes and protects the two species, the International Union for Conservation of Nature and CITES, the treaty that regulates global trade in endangered wildlife, may follow suit, bringing new and urgently needed help to the highest-risk elephant populations.

An endangered listing would also tighten restrictions on the import, export and sale of ivory products to, from and in the United States. After China, the United States is the world’s second-largest market for ivory, with the legal trade in old ivory being used as a cover for illegal trade in new ivory. Last month, a senior Chinese wildlife official pledged to end the ivory trade if the United States does, too.

That means American action on reclassifying African elephants now could lead to a transformation of the way the planet’s two largest economies — which also happen to be its two largest ivory consumers — are handling the crisis of the animals’ slaughter.

We should act now, before it’s too late.