The Secret Life of Trees
This month’s issue of Oryx-The International Journal of Conservation is dedicated to tree conservation. In this blog, Dave Gill and Rob Loveridge discuss the special issue and pay tribute to the scientists whose work is guiding the conservation of the ‘charismatic megaflora’.
“On close inspection trees reveal all sorts of secrets. In 2015 alone, scientists have discovered that different species communicate and send food to each other through their roots systems; that tropical rainforests are home to an astounding 40,000-53,000 tree species; and that 182 ‘carbon-hungry’ species store more than half of the Amazon rainforest’s carbon.
Such research breathes new life into how we think of trees, and reminds us that the stories behind their existence are rarely simple.
But more vitally, the work of tree conservation scientists also helps to define where and how best to take action for the world’s 9,000 tree species at risk of extinction.
Identifying trees under pressure
This month’s Oryx cover features the Tropical Andes, where >60% of the tree species assessed by Tejedor-Garavito et al. were deemed threatened with extinction, principally by habitat loss. The Red List they produced will guide conservation action in the Andean region, but the process of Red Listing, here and elsewhere, is hampered by a shortage of good data. To date we know the conservation status of only 16% of the world’s trees. Newton et al. describe these challenges and propose an approach to accelerate Red Listing of trees, arguing that, with the advent of new computing and web technologies, now is the time to launch an assessment of all of the world’s tree species.
Coming to terms with habitat loss
A common thread through the articles is the impact of habitat loss. Rodríguez-Echeverry et al. revealed that the Patagonian cypress Fitzroya cupressoides lost 46% of its potential habitat within a period of 12 years. As smaller populations become increasingly surrounded by commercial plantations, their persistence depends on retaining connectivity between one another; thus land-use planning, targeted restoration and sustainable agriculture are all necessary parts of the solution.
Other trees are even further down the extinction vortex. With <1% of southern Brazil’s Araucaria forest remaining, many trees species there are rare, isolated, and failing to reproduce. Hoffmann et al. surveyed 68.7km of trails, locating seed-producing trees for 38 of 71 known rare or threatened species. They identified optimal timing of seed collection for these species, and their research is directly supporting species recovery projects across the landscape.
In Queensland, Australia, Brown et al. investigated the ecology of the Endangered Alectryon ramiflora, which in 2013 had only 26 individuals remaining. Because the species is dioecious (individual trees are either male or female, and never hermaphrodite) its persistence is particularly dependent on pollinators getting from A to B¾a real problem for such a rare species. Other key factors underpinning the recovery of wild populations include the presence of invasive weeds (which unexpectedly improved soil quality) and frugivorous birds (necessary if the species is to colonize new sites).
Animals and trees in it together
The interconnectedness of fauna and flora was highlighted to an even greater degree by David Beaune’s research in LuiKotale, Democratic Republic of Congo. Bonobos, the amorous cousin of the chimpanzee, are fruit fanatics, and one individual will disperse an estimated 9.1 tonnes of seed in its lifetime. Without this service, 95% of bonobo-dispersed trees failed to establish seedlings, and the future of these species therefore appears to be closely linked to that of the bonobo, itself threatened by hunting.
Making business scents
In the lower montane forests of Saint Lucia, Daltry et al. set out to solve a conservation dilemma: can local tappers continue to harvest a valuable aromatic resin from the lansan tree Protium attenuatum without further endangering the wild population? After testing a variety of tapping regimes on 298 healthy lansan trees, the authors identified methods that could boost resin yield without harming tree growth, condition or mortality. These methods are now being adopted as part of a national management plan for the species, under which tappers are licensed to use lansan-friendly methods in dedicated areas of forest.
Pulling together for tree conservation
With so many trees on the edge of extinction, Cavendar et al. describe how the botanic garden community can more actively participate in their conservation. The challenges are manifold, but the opportunities appear to be far greater. They point to the benefits of working together at a global scale, including improved coordination to match skills and resources to particular conservation problems, and the empowerment of gardens in biodiversity hotspots to participate in tree conservation locally.
The fate of the charismatic megaflora hangs in the balance, yet the articles in this issue of Oryx offer reasons for hope. Conservation approaches are working; supporting livelihoods and beginning the long process of recovery for trees on the very edge of extinction. The articles also show that there is real appetite from the global community to support field-based projects, whether it is through the acceleration of Red Listing, through the botanic garden community or through initiatives such as the Global Trees Campaign.
We thank all of the authors for their contributions to the special issue.”