As global leaders begin hashing out a global warming accord in Paris beginning next week, their efforts to tackle the enormous issue of deforestation was supposed to be boosted by a heralded, business-led effort to protect the world's tropical forests and combat climate change. But that program has so far failed to deliver progress and its sluggishness serves to highlight how complex the issue is, and how many barriers stand in the way.

The New York Declaration on Forests was supposed to help halve forest loss by 2020, but an initial assessment published last week by the Amsterdam-based consulting company Climate Focus along with a group of non-governmental organizations said deforestation has not slowed in the countries that signed the pact. Also, very few of the world's leading companies whose practices drive deforestation have changed their policies to begin to tackle the issue, according to a separate report published last week by the Global Canopy Programme.

The declaration was signed in September 2014 by 52 companies—including Unilever, Walmart and General Mills—as well as more than 30 countries and 100-plus subnational governments, indigenous groups and non-governmental organizations. They committed to 10 goals, meant to cut the world's forest loss in half by 2020 and end it by 2030.

"We are not on track to end the loss of natural forests," said Charlotte Streck, director of Climate Focus.

"We see a lot of action. We see pledges. We see programs. We see activity. It is not enough, however. More needs to be done," she said, while noting that battling deforestation is a massive challenge that can't be solved overnight.

The declaration was notable for its ambitious targets and rare collaboration among countries and corporations, and for tackling the root causes of deforestation, primarily corporate agriculture practices. The majority of tropical forest loss and degradation is driven by the production of only six commodities: palm oil, soy, beef, leather, timber, and pulp and paper, according to the Global Canopy Programme study.

Climate Focus reported that while there was progress in replanting trees on degraded land and an "increase in action on forests" since the declaration's signing, there are no signs that the annual rate of forest loss is slowing. (Indonesia, which recently surpassed Brazil as the largest contributor to deforestation, was a signatory; Brazil was not.) The Global Canopy Programme, meanwhile, found that only 8 percent of 250 "powerbroker" corporations—and less than 1 percent of the 150 leading lenders and investors in agricultural companies—have polices in place to eliminate or reduce deforestation.

The reports raise questions about what's standing in the way of efforts to preserve and restore forests, and what needs to happen at the Paris climate talks to accelerate the pace of change.

Deforestation accounts for about 10 percent of global man-made emissions through the razing and burning of trees. Because tropical forests are potent carbon sponges, stopping deforestation—and allowing damaged forests to recover—could deliver as much as 40 percent of the emissions cuts needed to keep global warming to 2 degrees Celsius.

Forests "are really, at this point, the only practical way to take CO2 out of the atmosphere to sequester carbon. All of the other possibilities are very speculative technologies that may work in 20 or 30 years or may never work," said Doug Boucher, director of climate research and analysis at the Union of Concerned Scientists (UCS). " If we are going to get to what the IPCC [Intergovernmental Panel on Climate Change] says is necessary—which is negative emissions, net carbon sequestration on a global basis in the second half of the century—forests are the only practical way to do it."

Ultimately, to stop deforestation at the rate envisioned in the New York declaration, nations meeting in Paris will have to unite to make protection of tropical forests a key component of any climate deal, forest experts say, and not rely only on corporate promises. Developed countries also will have to come up with the billions of additional dollars to persuade nation to keep their forests standing.

Progress in Paris would "serve as a bellwether for the fate of the [New York] declaration—and forests," Streck said in a statement, by signaling to companies that the world's governments are giving increased priority to saving forests.

She said, however, that if climate pledges going into Paris (known as Intended Nationally Determined Contributions, or INDCs), are any indication, "countries must take their role in tackling deforestation more seriously." Of the 122 countries that had submitted climate action plans at the time of the report's publication, only 40 had included specific actions on land use and forests in their targets.

Paris Talks: Forest Finance Key

The main forest protection mechanism under the UN climate regime is called REDD+ (short for, reducing emissions from deforestation and forest degradation plus conservation and sustainable management to enhance forest carbon stocks). The program would pay nearly 50 developing tropical nations to keep forests standing and is widely endorsed by wealthy and poorer nations.

REDD+ is already working through bilateral deals and multilateral funding. Norway, for example, has a bilateral agreement with Brazil that has provided the South American country $1 billion through REDD+ for keeping its forests intact. The 7-year-old program has been incredibly successful, helping the country reduce its rate of deforestation by 75 percent. Reductions in the rate of deforestation in Brazil have saved more than 33,000 square miles of forest since 2004, an area roughly the size of Maine, according to a study published last year in the journal Science.

Other countries, including Germany and the United Kingdom, have suggested they may soon announce similar partnerships, according to Jonah Busch, a research fellow at the Center for Global Development who specializes in forests.

But while bilateral and multilateral funding is useful for pilot projects, many forest advocates say, it's no substitute for implementing and financing REDD+ at a global scale, which is necessary for radical change in slowing global warming. Crucial to achieving this, some say, is to prominently mention REDD+ in any Paris climate agreement and also to make clear the funding amounts that forest countries would receive under the deal after 2020, something the United States, European Union and other developed countries are opposed to doing.

Cutting the rate of deforestation in half, the goal of the New York declaration, would require $20 to $30 billion a year, significantly more than current pledges, which remain less than $10 billion a year, according to Boucher of the UCS.

"What is most important is that they come up with the money, that there is a substantial amount of pledges for funding for it," Boucher said. "We've had good progress on the rules and the mechanisms for REDD+ but we haven't had significant pledges for funding in the range that we really need." (Negotiators have made headway on safeguards that protect indigenous peoples and ecosystems under the scheme, but advocates say more needs to be achieved in Paris.)

Funding REDD+ could get some countries to increase their overall climate ambition, said Michael Wolosin, a managing director of Climate Advisers, a Washington D.C.-based consulting firm and an internal reviewer of the Climate Focus report. Indonesia, for example, one of the world's largest carbon polluters due to deforestation, peatland degradation and fires, pledged to cut its emissions by 29 percent but has said it would increase emission reductions to 41 percent if it gets international assistance, he said.

About 80 countries submitted carbon-cutting pledges with conditional commitments, according to Wolosin's calculations, and if met they would greatly increase the ambition of any Paris climate deal, he said. "It's quite a big chunk."