A newly formed alliance of green groups, government agencies and private companies has set for itself the ambitious goal of returning Brazil’s fragmented Atlantic Forest to nearly a third of its original size.

Often overlooked amid concern about the vast Amazon rainforest, the richly varied Atlantic Forest is considered one of the world’s most biodiverse areas—more so in places, acre for acre, than even the Amazon. Carved up for centuries as Brazil’s coastal development expanded and turned inland, the forest is estimated today to possess little more than 7% of its original area in blocks large enough to sustain a reasonable variety of species. However, hundreds of thousands of tiny forest fragments and degraded scrubland could add as much as 13% to this figure. So some 20% of the original 1.5-million-square-kilometer biome that existed prior to European settlement may already be in some sort of forest cover.

The core proposal of the new Atlantic Forest Restoration Pact is, by 2050, to restore native forest to a further 150,000 square kilometers—an area the size of Illinois—using a combination of unproductive farmland and areas which under Brazilian law should in any case be left undisturbed by human activities.

The pact, announced last month, brings together more than 50 organizations including non-governmental groups, institutions linked to federal, state and local authorities as well as corporate and private landowner associations. It does not include commitments of increased funding for the conservation work. Instead, the aim is to harmonize the many individual efforts to restore Atlantic Forest woodlands, pooling technical knowledge and providing annual updates of progress towards the target.

The coordinator of the pact, Miguel Calmon of the U.S.-based green group The Nature Conservancy (TNC), says much of the effort would involve helping landowners obey Brazil’s Forest Code, which requires all properties to retain native vegetation on 20% of their land, as well as on riverbanks, steep slopes, hilltops and near water sources.

“If we can create the mechanism and instruments to help landowners comply with the law, then at the end of the day we can achieve a common goal to have 30% of the original forest—which is really the minimum we feel is necessary to promote biodiversity conservation and to generate all the ecosystem services, especially water—for the millions of people living in the Atlantic Forest,” Calmon says.

The original Atlantic Forest biome extends some 3,000 kilometers (1,900 miles) along the Brazilian coastline and inland as far as Paraguay and northern Argentina. It includes major cities such as São Paulo, Rio de Janeiro and Salvador; a total of some 130 million people live within its boundaries, accounting for 70% of the country’s population.

So it is not surprising that this forest, positioned in the path of five centuries of settlement and development of Brazil’s eastern seaboard, has been sliced up to a far greater extent than the less accessible Amazon. Only recently have urban Brazilians begun to realize the value—and vulnerability—of this biodiversity treasure chest on their doorstep.

The term Atlantic Forest, or Mata Atlântica in Portuguese, actually refers to a mosaic of contrasting ecosystems ranging from just 3 degrees south of the equator to below the Tropic of Capricorn; and from the sandy restinga forests at sea level to mountain forests and grasslands up to an altitude of more than 2,700 meters at the highest point of Brazil’s coastal range.

This has given the biome an extraordinary variety of plant and animal life, unrivalled on the planet. Of the more than 20,000 plant species found in the Atlantic Forest, some 8,000 occur nowhere else in the world; it is also home to nearly 1,000 bird species, 372 types of amphibians, 350 fish varieties, 197 kinds of reptile and 270 known species of mammal.

Of the many superlatives linked to the Atlantic Forest, one staggering statistic stands out. In a survey of one of the richest parts of the ecosystem, in the state of Bahia, more than 450 different tree species were identified in a single hectare of forest. The entire United Kingdom is thought to have only 33 genuinely native tree species.

What qualifies the Atlantic Forest as a biodiversity hotspot is the combination of this staggering variety with a high level of threat, due to its location. The forest has felt the pressure of ever-growing human activity since the arrival in Brazil of Portuguese explorers in 1500—or arguably before then, as indigenous peoples arrived on the Atlantic coast and began making significant changes to the ecosystem.

The original forest has been devastated by successive cycles of exploitation of the region’s resources. There was the uncontrolled harvesting of Pau Brasil or brazilwood trees to create coveted red dye for the European textile industry (making this the only country to take its name from a tree); the clearing of large swaths of forest in northeastern Brazil for slave-worked sugar plantations; and the cattle-hide and coffee booms of the 18th and 19th centuries. Among the strongest pressures more recently was the felling of the interior forest of southern Brazil to make way for construction around such cities as São Paulo and Curitiba and for industrial-scale plantations of crops such as soy and sugarcane.

After all this buffeting through centuries of agricultural, industrial and urban development, the biggest surprise is perhaps that enough of the Atlantic Forest is left for it to be one of the powerhouses of global biodiversity. Even the fragmented remains of the ecosystem are estimated to account for as much as 8% of the total number of species on the planet.

The question is, for how long? Nearly 400 animal species in the region are currently judged to be under threat of extinction. And the most recent research on the state of the forest indicates just how fragile much of this biodiversity really is.

In the June issue of the journal Biological Conservation, devoted to the Atlantic Forest, a new study reveals that some 80% of the remaining ecosystem exists in fragments of less than half a square kilometer, and nearly half of it is less than 100m from the forest edge, leaving it highly vulnerable to pressures from the surrounding areas such as invasive alien plant species.

All this makes the task of restoring 30% of the forest a huge challenge. One of the principal aims of the new pact is to learn from 30 years of experience of forest restoration in the region, to establish which techniques work and which do not, so that money and effort is not wasted. For example, some early attempts at reforestation proved short-lived because only fast-growing tree species were used. Once they reached maturity, they died, and none of the slower-growing, larger varieties were coming up to replace them.

Recent restoration work has involved native species and more sophisticated approaches aimed at replicating the natural “succession” phases of a forest—for example, when a big tree dies and the race begins to capture the sunlight suddenly exposed. First to emerge are the “pioneer” species, quick-growing, spindly trees that shoot up to grab the light; underneath their partial shade comes the so-called secondary growth; and finally the “climax” species, the tortoises of this race that emerge inconspicuously in the undergrowth but become the mighty giants of the rainforest canopy.

For restoration efforts to be long-lasting, the recognized best practice involves understanding the dynamic architecture of a living forest, as well as the interactions with birds and mammals that disperse the seeds and help maintain genetic diversity. So when tree seedlings are planted in a cleared area, for example, it is vital to have a variety of species from each stage of succession. Knowledge of soil type and climate also is essential, and successful restoration involves various interventions such as control of ants and clearing of invasive grasses in the early stages of tree growth. It is hard, and it is expensive.

The president of the Atlantic Forest Biosphere Reserve, Clayton Lino, is acting as a focal point for all the disparate groups involved in this pact. He admits that it is impossible to recreate all the features of the original forest, but believes that many of the important functions of the ecosystem can be restored by connecting and expanding the existing fragments.

“I think it is realistic and ambitious at the same time,” Lino says of the 30% target. “Realistic because we need to do this, and we have the potential areas and the potential partners. Many people want to protect and restore these areas. On the one side we have the law and its enforcement, and on the other we have the will. Together, we can do this.”

An important part of the restoration strategy will be to involve some of the large, corporate landowners keen to present an environmentally responsible face to the world. For example, big sugarcane estates faced with European doubts about the sustainability of the ethanol they produce now have good commercial reasons to ensure that they restore forests on the 20% of their land they are required by law to keep undisturbed.

Restoration efforts also are being undertaken by large timber companies growing exotic eucalyptus and pine for the pulp and paper industries. These companies, which were tainted in the past for replacing native forest with monocultures, are now involved in some of the biggest projects of Atlantic Forest restoration.

A major question hangs over the pact, however. Even if the targets for restoration are realistic—a big if for conservation experts—the initiative is launched at a time when Brazil’s forest-protection laws are under pressure as never before. As recently as March, the legislative assembly of Santa Catarina—currently the state with the highest rate of Atlantic Forest destruction—voted to relax the rules on preserving riverside and slope forests, under pressure from the agricultural lobby. (See related story—this issue.)

The Nature Conservancy’s Calmon says this decision was made in the very state that suffered disastrous floods and landslides at the end of 2008, with the death toll due at least in part to the construction of houses on steep hillsides where forests were supposed to have been protected. Moves are also under way in the Brazilian Congress to make the federal Forest Code more flexible.

“What we as a coalition of NGOs, [the] private sector and governments and landowners can show to society is that complying with the forest code right now, in the Atlantic Forest, is a much better solution in the long term than not to comply with it,” says Calmon. “Our job is to show them that if you can really tie what you are trying to do to tangible benefits to business, to the people, maybe we will have a chance to minimize some of the pressure on the forest code. But I agree it is a big challenge.”