With smoke from forest fires filling the air and a chainsaw roaring in the distance, a Huon tree kangaroo clambers anxiously above us in the tree-tops. Will this spectacular animal — an endangered inhabitant of New Guinea’s highland rainforests — have a home in the future?

These endearing animals, along with other local wildlife, are of great cultural importance to the local indigenous people and have sustained people living in the region for thousands of years. But their numbers are dwindling, as the pressures of a rapidly growing human population, habitat loss and over-hunting have taken a severe toll.

Across the tropical world, wildlife are facing similar perils. The Tropics account for 40% of the Earth’s surface area, but host more than 80% of its terrestrial biodiversity, 21 of 35 global “biodiversity hotspots” (threatened areas with unusually high diversity and many unique species), and more than 90% of the planet’s coral and mangrove diversity.

Much of this extraordinary natural diversity is in danger.

The new State of the Tropics Report found that for all major groups assessed, the Tropics have the highest number of threatened species. Some regions have more species at risk than others, with especially high numbers under threat in tropical Asia, the Amazon and island nations.

Threats to tropical biodiversity

Species in the Tropics are inherently more vulnerable to changes in their environment because they tend to occupy small geographic ranges, be naturally rarer and be specialised to deal with a narrow range of environmental conditions.

Tropical biodiversity is affected by a range of threats, often acting in different combinations to affect species differently. Habitat loss and degradation are among the most significant.

The loss of forests is particularly concerning, as they are home to so many species. Although deforestation rates have slowed in most tropical regions since 2000, losses remain large and are ongoing. Most are due to land use change, including conversion of forests to agriculture and resource extraction, particularly from forestry and mining.

The establishment of new transport networks associated with such activities, especially roads, also opens up large areas to other destructive impacts such as hunting and illegal logging, as well as facilitating the spread of introduced species.

But the threats to tropical animals and plants aren’t just happening on land.

Exploitation of marine food resources in the Tropics has grown rapidly over the past 60 years, due to greater demand for seafood from a growing and increasingly wealthy population, as well as increased fishing by international ships. Threats to coral reef systems have also increased, with more than half the world’s reefs considered to be at medium or high risk of damage.

Known unknowns

A lack of knowledge of tropical biodiversity is a major obstacle. We haven’t yet found most species, let alone studied their biology or assessed their conservation status.

A recent analysis suggests current extinction rates of species are 1000 times greater than the “natural” background rate. Even this is likely to be an underestimate, given that rates of extinctions are likely to increase with improved knowledge, because species we’re yet to discover are more likely to be rare or have a restricted range to begin with.

Not only is tropical biodiversity least known and most imperilled, but relative annual investment allocated to its study and protection in developing tropical countries is up to 20 times lower than in developed nations.

As well as benefitting from the global goods and services that tropical biodiversity provides, an increasing proportion of land in the Tropics is used to produce goods such as timber, biofuels, palm oil, beef and mining resources for export markets to developed nations.

So while many developed nations may boast of improvements in their own national conservation efforts, their ecological footprints are in fact growing as they export their impacts to poorer nations in the tropics.

Overlaying these threats and challenges is the spectre of climate change. Never mind polar bears: tropical biodiversity is much more likely to be impacted by climate change, which will also exert greater pressures on tropical communities through impacts on human and food security, renewable water supplies, rising sea levels and vector borne diseases.

Conservation of tropical biodiversity

Protected areas are the backbone of biodiversity conservation efforts worldwide. They provide refuges that protect species and habitats, sustain key natural processes and maintain ecosystem services essential to human well-being.

Globally the area allocated to protection has increased significantly in recent decades, with the greatest growth in the Tropics. But are protected areas alone enough to maintain biodiversity? At present, probably not. The current protected area system is unevenly distributed and not ecologically representative.

Protected areas don’t always adequately protect biodiversity either. Take Kakadu National Park, one of Australia’s biggest and best resourced national parks. In the last couple of decades, Kakadu has seen a rapid and extensive decline in native mammals, suggesting that even well-resourced protected areas in rich countries may not suffice.

It points to the critical need to not just set aside land, but to monitor and manage protected areas for biodiversity far more intensively and effectively, particularly in places prone to illegal encroachment and exploitation.

Local conservation champions

Close collaboration with local communities is essential. Such partnerships need to align conservation goals with local people’s aspirations and economic realities. This “bottom up” approach typically costs more and involves more work in the short-term, but tends to be more effective in delivering lasting outcomes that work for people and for nature.

Encouragingly, there are a growing number of examples of effective community-based intiatives worldwide, such as the YUS Conservation Area, Papua New Guinea’s first major protected area, and the winner of the Equator Prize 2014 for conservation and sustainable community development.

The world faces enormous population pressures in coming decades. Through the alleviation of poverty and improved health and education outcomes – particularly for women – population growth rates have been declining.

Nevertheless, the UN predicts the world population will peak at 11 billion this century, with most people living in the Tropics. By 2050, the region will be home to about half the world’s population, and 60% of the world’s children.

Meeting the food and energy needs of a larger and increasingly wealthy population will put unprecedented pressures on biodiversity and natural resources. Developing sustainable practices – including improving agricultural technologies and policies, reducing reliance on fossil fuels, limiting destructive road expansion and establishing an effective protected area system – are all priorities.

Tropical nations can play a leading role in developing sustainable pathways. But effective progress will require addressing current imbalances in resource allocation to developing nations, and greater recognition of the role of the entire global community in limiting impacts on tropical nature.