If there’s one number worth paying attention to in the fight to protect nature, it’s this: $700 billion.

That’s the sum in US dollars that experts say we need each year — in addition to more than $100 billion the world is already spending — to stop the decline of animals and ecosystems and all the services they provide, from creating clean water to pollinating commercial crops. That money would go toward ramping up urgently needed conservation efforts including replanting forests and making farms more wildlife-friendly.

But how exactly countries can raise that money is still an open question, and one that’s central to the modern environmental movement. Beginning Monday, world leaders will meet in Cali, Colombia, for a major United Nations event known as COP16, the world’s most important conference concerned with protecting plant and animal life. Finalizing a plan to funnel more money into the environment is one of the event’s main goals and one of its most enduring sticking points.

The good news is that $700 billion is actually not that much. At least compared to global GDP, which amounts to more than $100 trillion. And it’s less than the US alone spends on its military each year.

Then again, most countries don’t prioritize conserving nature compared to things like health care and infrastructure, which tend to yield more obvious and immediate benefits. While people understand the problem of a crumbling freeway, it can be harder to perceive the loss of wildlife, which may occur over decades. Plus, it hasn’t been easy for companies or financial firms to invest in ecosystems in the same way they might back, say, a renewable energy project; the value of healthy ecosystems is still overlooked and grossly underpriced.

So coming up with $700 billion will be a challenge, even though the return on that investment is priceless. Every basic human need, from food to water to shelter, depends on ecosystems and animals that compose them. This is about sustaining human existence.

By most measures, populations of plants and animals are collapsing, and they have been for decades. Coral reefs are disappearing, as are tropical forests. Animals are going extinct. It’s bleak.

The world’s best defense against these alarming declines is a UN treaty called the Convention on Biological Diversity, which aims to protect nature. Every two years, the convention hosts a conference with all of its members, or parties — which includes leaders from nearly every country, except the US — called COP.

In late 2022, during COP15, countries met in Montreal and agreed on a groundbreaking new plan to stop the global decline of nature. The plan, known as the global biodiversity framework, lays out 23 targets that countries need to achieve by 2030, including a goal to conserve at least 30 percent of all land and water on the planet. It’s ambitious.

To meet those targets, countries — and especially poorer nations — need more money, to the tune of $700 billion per year, according to the framework. Experts say this number comes from an influential report published in 2020 by Cornell University and two nonprofits, the Nature Conservancy and the Paulson Institute. The report estimated that countries and companies currently spend about $133 billion a year on protecting wild animals and places, such as by restoring habitat. Yet in order to truly safeguard ecosystems, including conserving nearly a third of the planet’s land and water, they’ll need to spend more like $844 billion a year, the report found.

Rounded down, the gap in spending is $700 billion a year. This is often referred to as the biodiversity finance gap, and this number is used in the highest-stake negotiations to safeguard the natural world.

The biggest chunk of that $700 billion is meant to target agriculture through a suite of efforts that would make farms and ranches more sustainable. Agriculture, which drives about 90 percent of deforestation in the tropics, is by far the largest driver of animal declines globally — not hunting or poaching. Industrial farms not only replace native grasslands and forests with vast fields of crops but also often rely on pesticides and fertilizers that harm animal life. Making farms more sustainable, such as by using natural pest controls, can come at high upfront costs to the agriculture industry.

Setting up new parks to protect land, restoring forests, and eradicating invasive plants like cheatgrass also costs many billions of dollars a year, the report found. Together these conservation efforts contribute to the $700 billion figure.

The 2022 plan to save nature laid out what are essentially four main ways to close that funding gap.

The first is to ramp up money that wealthy countries and philanthropists give or loan to poorer nations for conservation, either directly or through big development banks like the International Monetary Fund and the World Bank. This is foreign aid. The second is increasing the amount of money that national governments spend on protecting nature, such as through their environmental or agriculture ministries. The third avenue is encouraging the private sector, including corporations and investors, to spend more on conservation efforts.

These three categories are meant to raise $200 billion a year by 2030, according to the plan.

The fourth way to close this gap is to shut off incentives that directly harm the natural world. Indeed, the remaining money — $500 billion a year — is meant to come from phasing out or repurposing harmful subsidies. Subsidy is a somewhat squishy term that refers to benefits that a government provides to commercial industries, such as the agriculture and oil and gas industries. Often this is in the form of direct payments but it can also include things like tax breaks and government research that ultimately benefits companies. The idea is to repurpose subsidies so that they incentivize efforts to safeguard nature. “Subsidy reform represents the single biggest opportunity to close the funding gap,” authors of the 2020 report wrote.

During this year’s UN negotiations in Colombia, world leaders will try and figure out how to make this happen.

Let’s start with foreign aid, the money that would go from rich countries to poor ones. While it’s ultimately a very small piece of the pie, these payments are politically fraught. Many low-income countries, such as those in central Africa, hold much of the world’s plant and animal life, yet they often lack the resources to protect it. Meanwhile, the industries threatening that natural abundance, such as metal mining, are often stoked by wealthy nations. So developing countries say it’s only fair that wealthy countries help foot the bill for conservation.

In 2022, global leaders landed on a deal. According to the biodiversity framework, rich countries like Canada and Japan will pay developing nations at least $20 billion a year for conservation by 2025 and $30 billion a year by 2030. And this money has already been flowing: Aid for conservation in developing nations reached $15.4 billion in 2022, according to the Organisation for Economic Co-operation and Development (OECD), which tracks spending. The bulk of this money comes from development banks and direct payments from wealthy to poor countries. That’s a big increase from 2021, when aid for conservation reached $11.1 billion.

This is promising at face value: Rich countries are less than $5 billion from their aid goal. But the scale of biodiversity loss in the Global South — lower-income countries that are typically south of the equator — will almost certainly require a much larger increase in funding, said Brian O’Donnell, who leads the environmental group Campaign for Nature. The other problem is that much of that aid money is in the form of loans, “which is problematic, given the massive debt that we’re seeing in much of the Global South,” O’Donnell said.

A much bigger portion of the $700 billion gap will need to come from national governments — what individual countries raise and spend within their borders. Environmental ministries, for example, will need to put more resources toward stopping cattle ranchers from razing the rainforest, whereas agriculture agencies might have to fund more sea patrols to prevent overfishing.

A key question is where all that money will come from. Governments could redirect spending from other departments. They could impose new taxes on products like pesticides and close tax loopholes. They could also raise more money from their natural resources, such as by increasing entrance fees for national parks, said Onno van den Heuvel, who leads a UN nature finance project called BioFin. BioFin helps countries come up with money for conservation. “Protected area budgeting is one of the areas where there’s a lot more that countries can do,” he told Vox.

Then there’s the role of the private sector — which is where things get more complex.

There’s a whole host of new projects designed by governments and NGOs to get companies and investment firms to fund conservation. An initiative called the Taskforce on Nature-Related Financial Disclosures (TNFD), for example, was created by the UN and nonprofit leaders to help companies and investors identify how their profits depend on healthy ecosystems. The thinking is that firms are more likely to protect nature as part of their business if they know how much they depend on it. For example, a company that grows chocolate might invest in protecting insects when they learn their cacao crops depend on them for pollination. A different project called the Tropical Forest Finance Facility (TFFF), which is still under development, would help direct money from wealthy countries and investors to countries that have successfully stemmed deforestation.

Yet another large effort, hotly debated among environmental leaders, aims to raise money for nature from something called digital sequence information (DSI). DSI is essentially the genetic material from living organisms, in digital form. All kinds of companies, such as pharmaceuticals and agriculture firms, rely on that data to create commercial products. A proposal on the table at COP16 would funnel money from industries that rely heavily on DSI into conservation, especially in the Global South.

The last bucket of funding — which would pull money from subsidy reform — is even trickier.

We’ve established how important it is for world leaders to raise $700 billion to protect nature. Now consider this: Countries are collectively spending $1.25 trillion — yes, trillion — on subsidies for agriculture, fishing, fossil fuel development, industries that are known to erode biodiversity, according to a 2023 report by the World Bank. Other reports suggest that the value of harmful subsidies is much higher.

This means that countries are subsidizing environmental harm on an enormous scale.

Environmental leaders want to change this. In the 2022 biodiversity framework, they agreed to reduce subsidies that harm the environment by at least $500 billion a year by 2030.

But the challenge they face is immense, and they’ve failed at it before. In 2009, leaders of the G20, which run the world’s largest economies, agreed to phase out fossil-fuel subsidies in the medium term, but such kickbacks have since ballooned. And in 2010, nearly all countries agreed to a set of environmental goals, known as the Aichi Targets, including phasing out subsidies that harm nature, by 2020. They didn’t meet that target (or any other one of the 20 Aichi Targets, for that matter).

Experts say there’s really only one way to make this work: Instead of getting rid of subsidies, countries should redirect them toward commercial efforts that make companies more sustainable. In other words, subsidies should incentivize conservation, said Andrew Deutz, a policy and finance expert at the World Wildlife Fund. Governments could, for example, deepen tax breaks for farmers who restore pollinator habitat instead of subsidizing the cost of pesticides.

“We don’t want to remove subsidies from the agriculture sector,” Deutz said. “We’re trying to change the behavior that’s incentivized by the money.”

Some countries have made progress on subsidy reform, said the UN’s van den Heuvel. At least a dozen countries including Colombia have identified their subsidies that harm nature, which is the first step, he said. “There is better momentum than in the last decade,” he said. “Now countries are willing to investigate.”

Yet policy experts still worry that it will take decades to reform these systems. Part of the problem is that most governments are siloed — the agriculture and environmental ministries don’t talk to each other — and they often work against each other, said Carlos Manuel Rodríguez, the former minister of the environment and energy in Costa Rica. Environmental officials might be trying to protect pollinators while agricultural officials are subsidizing pollinator-killing pesticides.

And while many companies want to reduce their environmental footprint, they often don’t even know what subsidies they’re receiving, said Eva Zabey, the CEO of Business for Nature, a group that helps align corporate and environmental goals. “It will be a messy topic,” Zabey said of trying to reform subsidies.

Nonetheless, world leaders agreed that the majority of money needed to close the finance gap — more than 70 percent — is meant to come from subsidy reform. O’Donnell says it’s “one of the biggest weaknesses in finance for the biodiversity framework.” Andrew Deutz of WWF echoed his concerns, saying that the number senior negotiators are most worried about is the $500 billion in subsidy reform.

“It’s the biggest number,” Deutz said, “and perhaps the most politically difficult one to address.”

Raising more money is a challenge, but there are also problems that money won’t fix.

One has to do with how aid funding is managed. Much of the money that wealthy nations put toward conservation in developing countries is managed by an organization called the Global Environmental Facility (GEF). GEF disperses money to these low-income countries. Yet many of those countries say it’s burdensome to access GEF funds and argue that it’s controlled largely by wealthy nations. Developing countries want a new fund that gives lower-income countries more control.

“It’s not about developing countries begging for money,” said Lim Li Ching, a senior researcher at the Third World Network, which advocates for developing countries. “It really is about equity.”

Manuel Rodríguez, who now runs the GEF, says that concerns about how GEF manages foreign aid are misplaced. He says that donor countries have more power in determining where money goes “for evident and obvious reasons.” Blaming GEF, he said, is a political tactic employed by large, biodiversity-rich countries to gain more control over how funds are dispersed.

Policy experts also point out that building new funds distracts from the main objective: to raise more money. “We have created a global myth that creating a new funding mechanism therefore means more funds,” O’Donnell said. “Just because you create a mechanism to distribute funds doesn’t mean someone is going to fill up the coffers.”

Concerns about international aid tie into a much more fundamental problem of how global financial institutions are structured and the inequalities they perpetuate.

Much of the current environmental destruction takes place in poorer regions of the world — the Global South, for the most part. Industries in places like Bolivia and the Democratic Republic of the Congo are destroying acre upon acre of forests. These countries are often blamed for that destruction; it’s their weak policies or poor enforcement that’s failing to restrict harmful activities.

But some scholars argue that much of the responsibility lies with the world’s big aid institutions, including development banks. These organizations, which lend money to poor regions, especially in a time of fiscal crisis, are governed by wealthy, or donor, countries. And the support they provide — whether loans or a restructuring of debt — can fuel the very industries that destroy the environment, including industrial agriculture, according to a recent report by the University of British Columbia, Third World Network, and a progressive think tank called the Climate and Community Project.

For one, poor nations are, on the whole, in a huge amount of debt from these international lenders. The UN estimates that an eye-popping 3.3 billion people live in countries with governments that spend more on debt interest payments than on the education or health of their citizens.

Think about that statistic for a minute. It’s extreme: That’s about 40 percent of the world’s population.

And all that debt they carry creates an incentive for countries to make tons of money quickly, which tends to fuel resource extraction. That’s partly because countries often need foreign currency to repay those debts, which they commonly earn through export commodities like soy that harm native landscapes. Frequently it also leads to countries loosening regulations on development in order to grow export industries.

On top of all of that, loans often come with austerity measures that require countries to clamp down on public services. These cutbacks are often imposed on environmental agencies that enforce rules to safeguard nature. “The international financial architecture continues to supercharge extraction,” said Jessica Dempsey, a researcher at the University of British Columbia and one of the report authors. “That’s just making the problem worse and worse.”

It’s hard to imagine solving environmental problems simply by raising more money. World leaders also need to upend deeply rooted systems that perpetuate wealth inequality and the harmful industries it fuels. There are a lot of ideas floating around about how to do this, from overhauling how lenders like the IMF and World Bank are governed to debt cancellation and closing tax loopholes.

But that won’t happen overnight.

“I mean, it’s a huge, huge task,” Lim said. “But then it’s also an imperative. If we don’t address it, we’ll just be [working] around the edges of making a difference.”