On this Earth Day, it's still an open question to what degree our planet will remain habitable in the coming years.

To increase chances that it will, it's critical to replace fossil fuels with renewable energy internationally, and on the individual level for each of us to reduce carbon emissions stemming from individual habits. These are among the main takeaway messages from the UN's Intergovernmental Panel on Climate Change report released on April 4.

That report led to worldwide headlines about the climate crisis. Moral philosopher and former journalist Elizabeth Cripps offers an equally urgent message in What Climate Justice Means and Why We Should Care, published in the U.S. last week: Efforts to contain global warming will succeed only if they are coupled with policies of climate justice.

Why is this so? Let's start with exactly what "climate justice" means. Climate justice rests on two major premises. Rich nations contribute disproportionately to global warming, leading to violations of human rights across the world. Poor, vulnerable people suffer the brunt of extreme weather including heat waves and so-called "natural" disasters that are actually human-caused. Second, those rich nations, and wealthy individuals too wherever they live, must take extra responsibility for fighting this crisis while keeping uppermost in mind the needs of those most grievously affected.

Climate change, Scripps says, is "a morally impermissible harm" and a "failure to protect the most vulnerable." It's a specific, situated harm: The wealthiest 1 percent of the world's population has produced more than twice as much carbon emissions as the poorest half of the world. Cripps brings home the point: "Even if the poorest 90 percent of people in the world dropped their greenhouse gas emissions to zero tomorrow, the carbon budget would be used up only a few years later than it would otherwise have been."

It's not that the richer countries escape climate consequences, of course. Events like the recent flash floods in Western Europe, bush fires in Australia, wildfires in the American West, and severe hurricanes in U.S. waters make that clear. But in the global south, Cripps says, the toll of extreme weather has been even worse going back decades, and the future looks catastrophic: The World Bank predicts 86 million "internal climate migrants" in Sub-Saharan Africa by 2050, 40 million in South Asia, and 17 million in Latin America.

Cripps yearns for us to see beyond these alarming statistics. "Envisage," she asks, each person hidden within these numbers, "with their own interests and plans for the future, their favourite foods and favourite jokes — before they're dehumanized, in your mind, by the scale of the tragedy." Shouldn't we care about 11-year-old Maroof Hussein in Bangladesh, whose school and house were flooded and whose 8-year-old friend drowned? Shouldn't it matter to us, the fate of disabled people the world over who are not able to flee from a flood and face extra risk?

As an anthropologist, I especially appreciated aspects of Cripps' analysis that often aren't emphasized. Alongside individual lives and well-being, "history, community, culture, unique knowledge" also may vanish. People living in small island states stand to lose all these things as the ice melts and their homes disappear. Women of color face outsized risk. Many indigenous women's lives, for instance, "revolve around flora and fauna, land and water, putting them especially at the mercy of rising temperatures."

Further, animals are included: "Justice for non-humans is not so much an 'extra' question as an inseparable part of the bigger picture." Animal species face heightened extinction risk because of global warming, and more than this, individual animals suffer. Ecologically, humans and nonhumans alike require a functioning environment to thrive, and our fates are connected. Plant-based eating is a key goal; animal agriculture contributes heavily to global warming as well as to animal suffering.

Occasionally I wished for a more penetrating explanation of her points. The rich, Cripps declares, "includes everyone living a comfortable life, wherever they are. In country terms, it means the global north." But is it helpful to conflate the comfortable with the rich? And despite this statement, it's clear that Cripps doesn't intend to ignore the global north's poor.

Cripps successfully argues her central point: Climate policies won't succeed if climate justice isn't at their forefront. What, then, is to be done? Cripps focuses on the goal of limiting temperature rise to 1.5 degrees C, even while noting that already by 2019, we had exceeded 1 degree. Three primary goals are mitigation, adaptation, and compensation.

Solutions that require international cooperation and personal-level commitment in a close choreography often fall under the heading of mitigation: reducing greenhouse gas emissions, pulling greenhouse gases from the atmosphere, investing in renewable energy, figuring out how to store carbon, moving towards that plant-based eating and away from air travel.

Sadly, little comfort is to be found here: all indicators suggest mitigation won't be enough. Needed will be floodwalls, shelters against extreme heat, and new ways to grow food and protect crops: that's adaptation and in order to do it properly, the most vulnerable communities must be prioritized. So it is too with compensation, ensuring that victims of the climate crisis are helped financially to rebuild their lives. Though a "last resort," compensation is a "morally necessary one."

How might mitigation, adaptation, and compensation be achieved? Cripps again spotlights past harms, especially racist ones. Wealthy corporate-level polluters like the oil, gas, and coal companies must pay the most — and those of us who owe our privilege to acts of violence and oppression must contribute too. A carbon tax could be levied most heavily on luxury practices like first-class air travel, space tourism, or driving sports cars. In reducing carbon emissions, each one of us must "keep trying until the costs to us are 'significant'." (Though ill-defined, "significant" is a threshold we recognize when we reach it. See Kim Stanley Robinson's The Ministry of the Future for a gorgeously rendered fictional account of what governments and private citizens can accomplish when they get serious about living differently in the face of disastrous global warming.)

Cripps' argument, a timely update to former President of Ireland Mary Robinson's earlier linking together of climate justice and human rights in her book Climate Justice: Hope, Resilience, and the Fight for a Sustainable Future, makes fine, inspirational reading. What Climate Justice Means and Why We Should Care can valuably be paired with a book publishing on Earth Day: Brian Kateman's Meat Me Halfway.

Kateman, an architect of the reducetarian movement, amplifies Cripps' plea for all of us to eat less meat and dairy. It's excruciatingly hard for many people to quit those foods, he notes, explaining the ways in which industrial animal agriculture "does all it can to keep us hooked on meat." For those who can't quit, seriously reducing intake of those foods makes a positive contribution. Kateman's insistence that we muster the collective will to end the factory farming that causes great suffering both to animals and to human communities dovetails beautifully with Cripps' call for environmental justice.

Barbara J. King is a biological anthropologist emerita at William & Mary. Animals' Best Friends: Putting Compassion to Work for Animals in Captivity is her seventh book. Find her on Twitter @bjkingape