Ecology biased against non-native species?
Nature authors: End bias, focus on impact, function rather than origin
The recent field of invasion biology faces a new challenge as 19 eminent ecologists issue a call to "end the bias against non-native species" in the journal Nature.
Often called aliens, hitchhikers or invasives, some scientists say that non-native species could just as easily be coined "abductees" whose transport links to activities by humans.
The authors of the Nature comments section note that assumptions that "introduced species" offer only deleterious impacts are misguided and "that human-induced impacts, such as climate change, nitrogen eutrophication, urbanization and land use change are making the native-versus-alien species dichotomy in conservation increasingly meaningless."
Mark Davis, lead author and professor with Macalester College in Saint Paul, Minnesota, says that a nativism perspective – native species equals good, non-native species equals bad – has dominated conservation efforts over the past few decades. He points to a number of ecologists, "including those who rightly could be called legendary for their contributions to the field over the past decades, who believe there has been way too much ideology and not enough good science associated with the anti-non-native species perspective."
The authors believe that a shift in the field is needed to consider outcomes and impacts of an organism on an environment rather than focus on native origins.
"Scientists who malign introduced plants and animals for thriving under favorable conditions seem to be disregarding basic ecological and evolutionary principles," say Matthew Chew, an ecologist and historian of invasion biology, and Julie Stromberg, a plant ecologist, with Arizona State University. "Evaluating whether a species 'belongs' in a particular place is more complicated than just finding out how and when it arrived."
Scientific studies show that while some introduced species have resulted in extinctions, not all natives are beneficial, as in the example of the Pine Bark beetle, which is decimating North American pine forests.
Chew and Stromberg have studied the impact of the non-native species in riparian ecosystems, most particularly tamarisk trees in the Southwest United States. Introduced to control erosion, Chew and Stromberg consider its continued perception as a pest species, water consumer and invader overplayed, while research shows its ecological role and ecosystem services have been undervalued. They point to outmoded perspectives and continued deference to outdated science as playing strong roles in negative perceptions of the species and intensive investment in eradication efforts. Recent discoveries have found that tamarisk in fact provides nesting habitat for birds, including the endangered Southwestern willow flycatcher, and that regional water management and climate change increasingly favor tamarisk over once-common cottonwoods and willows.
While the introduction of non-native species was noted as early as the 1620s, by Sir Francis Bacon, the field of invasion biology arose as an ecological approach as recently as the 1980s and 90s, inspired by Charles Elton's 1958 The Ecology of Invasions by Animals and Plants. More recent appraisals of Elton's research and publications by prominent ecologists now prompt a call for a change, these authors believe: "Invasion implies so many values. We need to consider the impact of these terms and approaches and how they affect scientific perception, public perception, and in turn, decision-making in conservation and restoration management."
Case study-Lantana camara in Tamilnadu,India
With emergence of conservation of biodiversity
as a major priority, conservationists require a broader knowledge about the
distribution, abundance and ecological service provided by Lantana camara . Conservation emphasis is now shifting from the
traditional species approach to wider issue by biodiversity conservation. We
have to work with a clear strategy rather than just saying that weeds have to
be uprooted and spend money on it. It is emphasized in the article 12 and 13 of
the convention on biological diversity to not only promote research on the
hidden potentials of Lantana camara but also to change popular perceptions based
on sound scientific research too.
There are a number of reports in support of Lantana camara utilization which provides shelter and vital
winter food for many native birds. A number of endangered bird species utilize Lantana camara thickets when their natural habitat is
unavailable. The Babblers inhabiting the river valleys and swamps at Mount
Kenya depend on small thickets of Lantana
camara for shelter and nest sites.
It is a known fact that the invasive plants now perform important ecological
functions. For example, fleshy-fruited invasive plants provide food that
supports indigenous frugivore populations. Sathyanarayana and Ramesh (2007)
reported that the intake of Lantana fruits by Grey jungle fowl, Gallus sonneratii at Gudalur, Theni Forest division, Western
ghats ,Tamilnadu. They have also observed the sambar deer, barking deer, mouse
deer, sloth bear, wild boar, black napped hare and insects were also using Lantana camara for food or shelter or nesting or escape
cover or roost. Bhat (2002) has reported
that it is far from truth that Lantana
camara is not eaten by native fauna.
He further stated, apart from its ability to grow and house many fauna and
flora, it is put to a lot of social uses. Further, Lantana camara is a major
nectar source for many species of butterflies and moths. Some unpublished work
has apparently suggested that several populations of Western ghat species now
rely on Lantana camara and a crash will be imminent if there is no
uncontrolled removal of this weed. The link between maintenance of Lantana camara thickets and biodiversity conservation has at
least been suggested (Dann, 2003). Lantana
camara is proposed to be providing
habitat essential to the promotion, or at least maintenance, of regional
biodiversity. To evaluate the effect of introduced species on species richness,
however, is to encounter a puzzling phenomenon. Both ecological theory and
observation confirm that “invasions may actually increase total species
richness” (Parker et al., 1999). It is emphasized that ecosystem level
consequences of Lantana camara invasion particularly on the biodiversity of
native flora are little understood and studies are needed to fulfill this
knowledge gap. There are, however, no recent data regarding the exact number
and incidence of these introduced invasive species in India. . The effects of
introduced species are so poorly understood and the record of predicting which
ones will cause problems is so bad that
one can question how much credence to place in a risk assessment (Schmitz and Simberloff , 1997 ) . There is
so much contingency involved among
organisms that we regard as invasive, that their study has to be essentially a
case by analysis.
al.(1998) reported that in many regions, Lantana camara has become a
dominant component of natural and agricultural ecosystems. He also stated that Lantana camara may provide Shelter and vital winter food for
many native birds. It is very important to note that a number of endangered
bird species utilize Lantana camara when their natural habitats becomes
unavailable. In Australia, the vulnerable black –breasted buttonquail, Turnix melanogaster, feeds and roosts in Lantana camara thickets. In central Kenya, where natural riverine thickets nave been almost
completely cleared, the endangered Hinde’s Babbler, Turdoides hindei, has become dependent on Lantana thickets, and
unless sufficient suitable natural habitat can be restored the survival of this
species depends on the retention of Lantana infestations.
In the view of the aforesaid facts , I [Dr.
M.C. SATHYANARAYANA] have suggested to
one of my M.Sc. Wildlife Biology students Mr.Thirumalainathan to undertake a short
term research work on the utilization of Lantana
camara by different groups of
animals at Gudalur Range , Theni Forest Division, Western Ghats ,
The studies carried out at Gudalur Range ,
Theni Forest Division , Western Ghats , Tamilnadu , revealed that different
species of Insects , Arachnids ,
Reptiles , Birds and Mammals utilized Lantana
camara for various activities . It
is interesting to note that totally 59 species of Insects (55) and Arachnids (4)
utilized Lantana camara . During the present study Insects and
Arachnids made 8826 visits (Butterflies 7643 visits and Spiders 53 visits) in
948 man hours spent. Other species such as ants, bees, flies, grasshopper,
beetle, bug, bumble bee and moth also utilized Lantana camara . The results showed that Insects and Arachnids
spent 24.25 hours / 948 Man hours spent. Of these butterflies spent 21.12 hours
/ 948 man hours spent. This shows that Lantana
camara plays a role in providing
ecological services to insects which in turn increases not only the diversity
of animals but also plant species.
It was also noticed during the present study
four species of Reptiles , viz., Southern green Lizard ( Calotes calotes ) , Garden Lizard ( Calotes versicolor ) , Rat Snake ( Ptyas mucosus ) and Green vine Snake ( Ahaetulla
nasuta ) utilized Lantana camara for shelter , escape cover and as a
substrate for basking . The reptiles spent most of their time basking (2.21
hrs) upon Lantana camara . This is
because the plant receives large amount of sunshine as it grows in the forest
During the study period 21 species of birds
utilized Lantana camara for foraging on flowers and fruits , perching and nesting site .The results
showed that Lantana camara provides a good
habitat for birds at Gudalur Range, Theni Forest Division , Western ghats ,
Tamilnadu . Four species of Mammals were found using Lantana camara as a shelter/
escape cover and for food. There had
been a number of sightings of Three
Striped Palm squirrel (Funambulus
palmarum) feeding on unripe drupes of Lantana
With a view of developing a better
understanding of the prevalent myth and value of Lantana camara , a consultation has to convened to bring together scientists , researchers , forest
officials , managers , policy decision makers and NGO . It is
necessary to prepare a backgrounder based on current review of research on Lantana camara . It is emphasized that
ecological level consequences ofLantana invasion particularly on the biodiversity of native flora and fauna are little
understood and studies are needed to fulfil this knowledge gap.
<strong><font face="arial black">Dr.M.C.Sathyanarayana</font></strong>
old address:Department of Zoology &Wildlife Biology
Mayiladuturai 609 305, Tamilnadu, India
NEW ADDRESS: 13/5 HARIDOASS I CROSS STREET
</strong></font>mcsa...@yahoo.com MOBILE NO 09442225759
[Non-text portions of this message have been removed]
|Dear Dr Sathya,|
It is indeed very true that many of the invasive species have the ecological importance for the other organisms especially birds of the invaded sites.
During our study at Abu Hills (Mt Abu WLS, Sirohi, Rajasthan, India) specially related to globally threatened species - Green Munia/ Green Avadavat (Amandava formosa) or endemic subtaxa - Tawny bellied babbler (Dumetia hyperthra abuensis) are well adapted for the habitats made by Lantana for their nesting and also feed on its fruits. Other then these - Red Spurfowl & Grey Junglefowl find their shelter in the Lantana bushes.
In the mammals - Sloth Bear eat Lantana fruits and is main cause of dispersion of its seeds through their droppings.
I will share one of our example of Lantana bushes:
On the Sunset Road at Abu Hills, the bushes were ideal habitats fro Tawny bellied babbler (TBB). If any birder/ researcher/ photographer interested in seeing the species, we use to take them at this spot. Unfortunately, in the move of clearing WLS from invasive species (Lanatana sp), Dept of Forest cleared the bushes and the small population of TBB was out. Now, if anyone has to see this species s/he has to travel in some deep areas.
When we informed Dept of Forest about this they immediately took action to clear those pockets only which is devoid of avifauna specially when it matters with the key bird species of Abu. For this step we appreciate the move and helped them further in clearing the pockets whenever we could got time to accompany with them.
Other than Lanatana there is Water Hyacinth. We found that this species is natural purifier and could play great role (in controlled manner) if used for the purification of the urban lakes. Unfortunately, on the name of beautification of lakes, these plants were completely removed from lakes and now one could see the pollution load in the lakes of Udaipur (Rajasthan, India)
Thus, I will appreciate the work. RSNH Team will help you if you make a move in the state.
Satya Prakash Mehra (Mr.), Ph.D.
Conservation Biologist, Rajputana Society of Natural History (RSNH)
+91-9414165690/ 9829144163 (Rajasthan, India)
--- On Fri, 10/6/11, J.M. Garg <jmg...@gmail.com> wrote: