ArticlePDF Available


Twenty-five years ago, the Union of Concerned Scientists and more than 1700 independent scientists, including the majority of living Nobel laureates in the sciences, penned the 1992 “World Scientists’ Warning to Humanity” (see supplemental file S1). These concerned professionals called on humankind to curtail environmental destruction and cautioned that “a great change in our stewardship of the Earth and the life on it is required, if vast human misery is to be avoided.” In their manifesto, they showed that humans were on a collision course with the natural world. They expressed concern about current, impending, or potential damage on planet Earth involving ozone depletion, freshwater availability, marine life depletion, ocean dead zones, forest loss, biodiversity destruction, climate change, and continued human population growth. They proclaimed that fundamental changes were urgently needed to avoid the consequences our present course would bring. The authors of the 1992 declaration feared that humanity was pushing Earth's ecosystems beyond their capacities to support the web of life. They described how we are fast approaching many of the limits of what the ­biosphere can tolerate ­without ­substantial and irreversible harm. The scientists pleaded that we stabilize the human population, describing how our large numbers—swelled by another 2 billion people since 1992, a 35 percent increase—exert stresses on Earth that can overwhelm other efforts to realize a sustainable future (Crist et al. 2017). They implored that we cut greenhouse gas (GHG) emissions and phase out fossil fuels, reduce deforestation, and reverse the trend of collapsing biodiversity.
Viewpoint XXXX XXXX / Vol. XX No. X BioScience 1
World Scientists’ Warning to Humanity:
A Second Notice
MAHMOUD I. MAHMOUD, WILLIAM F. LAURANCE, and 15,364 scientist signatories from 184 countries
Twenty-five years ago, the Union
of Concerned Scientists and more
than 1700 independent scientists,
including the majority of living Nobel
laureates in the sciences, penned the
1992 “World Scientists’ Warning to
Humanity” (see supplemental file S1).
These concerned professionals called
on humankind to curtail environmen-
tal destruction and cautioned that
“a great change in our stewardship of
the Earth and the life on it is required,
if vast human misery is to be avoided.
In their manifesto, they showed that
humans were on a collision course
with the natural world. They expressed
concern about current, impending,
or potential damage on planet Earth
involving ozone depletion, freshwa-
ter availability, marine life depletion,
ocean dead zones, forest loss, biodiver-
sity destruction, climate change, and
continued human population growth.
They proclaimed that fundamental
changes were urgently needed to avoid
the consequences our present course
would bring.
The authors of the 1992 declara-
tion feared that humanity was pushing
Earth’s ecosystems beyond their capac-
ities to support the web of life. They
described how we are fast approach-
ing many of the limits of what the
biosphere can tolerate without
substantial and irreversible harm.
The scientists pleaded that we stabi-
lize the human population, describing
how our large numbers—swelled by
another 2 billion people since 1992,
a 35 percent increase—exert stresses
on Earth that can overwhelm other
efforts to realize a sustainable future
(Crist et al. 2017). They implored that
we cut greenhouse gas (GHG) emis-
sions and phase out fossil fuels, reduce
deforestation, and reverse the trend of
collapsing biodiversity.
On the twenty-fifth anniversary of
their call, we look back at their warn-
ing and evaluate the human response
by exploring available time-series
data. Since 1992, with the exception
of stabilizing the stratospheric ozone
layer, humanity has failed to make
sufficient progress in generally solv-
ing these foreseen environmental chal-
lenges, and alarmingly, most of them
are getting far worse (figure 1, file S1).
Especially troubling is the current
trajectory of potentially catastrophic
climate change due to rising GHGs
from burning fossil fuels (Hansen etal.
2013), deforestation (Keenan et al.
2015), and agricultural production—
particularly from farming ruminants
for meat consumption (Ripple et al.
2014). Moreover, we have unleashed
a mass extinction event, the sixth in
roughly 540 million years, wherein
many current life forms could be
annihilated or at least committed to
extinction by the end of this century.
Humanity is now being given a
second notice, as illustrated by these
alarming trends (figure 1). We are
jeopardizing our future by not reining
in our intense but geographically and
demographically uneven material
consumption and by not perceiving
continued rapid population growth as a
primary driver behind many ecological
and even societal threats (Crist et al.
2017). By failing to adequately limit
population growth, reassess the role
of an economy rooted in growth,
reduce greenhouse gases, incentivize
renewable energy, protect habitat,
restore ecosystems, curb pollution, halt
defaunation, and constrain invasive
alien species, humanity is not taking
the urgent steps needed to safeguard
our imperilled biosphere.
As most political leaders respond to
pressure, scientists, media influencers,
and lay citizens must insist that their
governments take immediate action
as a moral imperative to current and
future generations of human and other
life. With a groundswell of organized
grassroots efforts, dogged opposition
can be overcome and political leaders
compelled to do the right thing. It is
also time to re-examine and change
our individual behaviors, including
limiting our own reproduction (ideally
to replacement level at most) and
drastically diminishing our per capita
consumption of fossil fuels, meat, and
other resources.
The rapid global decline in ozone-
depleting substances shows that we
can make positive change when we
act decisively. We have also made
advancements in reducing extreme
poverty and hunger (www.worldbank.
org). Other notable progress (which
does not yet show up in the global
data sets in figure 1) include the
rapid decline in fertility rates in many
regions attributable to investments in
girls’ and womens education (www., the promising
decline in the rate of deforestation in
some regions, and the rapid growth
in the renewable-energy sector. We
have learned much since 1992, but
the advancement of urgently needed
changes in environmental policy,
human behavior, and global inequities
is still far from sufficient.
Sustainability transitions come
about in diverse ways, and all require
civil-society pressure and evidence-
based advocacy, political leadership,
and a solid understanding of policy
2 BioScience XXXX XXXX / Vol. XX No. X
Figure 1. Trends over time for environmental issues identified in the 1992 scientists’ warning to humanity. The years
before and after the 1992 scientists’ warning are shown as gray and black lines, respectively. Panel(a) shows emissions
of halogen source gases, which deplete stratospheric ozone, assuming a constant natural emission rate of 0.11 Mt CFC-
11-equivalent per year. In panel (c), marine catch has been going down since the mid-1990s, but at the same time, fishing
effort has been going up (supplemental file S1). The vertebrate abundance index in panel(f) has been adjusted for
taxonomic and geographic bias but incorporates relatively little data from developing countries, where there are the fewest
studies; between 1970 and 2012, vertebrates declined by 58 percent, with freshwater, marine, and terrestrial populations
declining by 81, 36, and 35 percent, respectively (file S1). Five-year means are shown in panel(h). In panel(i), ruminant
livestock consist of domestic cattle, sheep, goats, and buffaloes. Note that y-axes do not start at zero, and it is important to
inspect the data range when interpreting each graph. Percentage change, since 1992, for the variables in each panel are as
follows: (a) –68.1%; (b) –26.1%; (c) –6.4%; (d) +75.3%; (e) –2.8%; (f) –28.9%; (g) +62.1%; (h) +167.6%; and (i) humans:
+35.5%, ruminant livestock: +20.5%. Additional descriptions of the variables and trends, as well as sources for figure 1,
are included in file S1.
Ruminant livestock
CO2 emissions
(Gt CO2 per year)
Temperature change
(billion individuals)
Dead zones (number
of affected regions)
Total forest
(billion ha)
Vertebrate species
abundance (% of 1970)
Ozone depletors (Mt CFC−
11−equivalent per year)
Freshwater resources
per capita (1000 m3)
Reconstructed marine
catch (Mt per year)
1960 1992 2016 1960 1992 2016 1960 1992 2016
g. h. i.
d. e. f.
a. b. c.
Viewpoint XXXX XXXX / Vol. XX No. X BioScience 3
instruments, markets, and other driv-
ers. Examples of diverse and effective
steps humanity can take to transition
to sustainability include the follow-
ing (not in order of importance or
urgency): (a) prioritizing the enact-
ment of connected well-funded and
well-managed reserves for a significant
proportion of the worlds terrestrial,
marine, freshwater, and aerial habi-
tats; (b) maintaining natures ecosys-
tem services by halting the conversion
of forests, grasslands, and other native
habitats; (c) restoring native plant
communities at large scales, particu-
larly forest landscapes; (d) rewilding
regions with native species, especially
apex predators, to restore ecological
processes and dynamics; (e) devel-
oping and adopting adequate policy
instruments to remedy defaunation,
the poaching crisis, and the exploi-
tation and trade of threatened spe-
cies; (f) reducing food waste through
education and better infrastructure;
(g) promoting dietary shifts towards
mostly plant-based foods; (h) further
reducing fertility rates by ensuring
that women and men have access to
education and voluntary family-plan-
ning services, especially where such
resources are still lacking; (i) increas-
ing outdoor nature education for
children, as well as the overall engage-
ment of society in the appreciation
of nature; (j) divesting of monetary
investments and purchases to encour-
age positive environmental change;
(k) devising and promoting new green
technologies and massively adopting
renewable energy sources while phas-
ing out subsidies to energy production
through fossil fuels; (l) revising our
economy to reduce wealth inequality
and ensure that prices, taxation, and
incentive systems take into account
the real costs which consumption pat-
terns impose on our environment; and
(m) estimating a scientifically defen-
sible, sustainable human population
size for the long term while rallying
nations and leaders to support that
vital goal.
To prevent widespread misery
and catastrophic biodiversity
loss, humanity must practice a
more environmentally sustainable
alternative to business as usual. This
prescription was well articulated by
the world’s leading scientists 25 years
ago, but in most respects, we have not
heeded their warning. Soon it will be
too late to shift course away from our
failing trajectory, and time is running
out. We must recognize, in our day-
to-day lives and in our governing
institutions, that Earth with all its life
is our only home.
We have been overwhelmed with the
support for our article and thank the
more than 15,000 signatories from all
ends of the Earth (see supplemental
file S2 for list of signatories). As far as
we know, this is the most scientists to
ever co-sign and formally support a
published journal article. In this paper,
we have captured the environmental
trends over the last 25 years, showed
realistic concern, and suggested a few
examples of possible remedies. Now,
as an Alliance of World Scientists
( and
with the public at large, it is important
to continue this work to document chal-
lenges, as well as improved situations,
and to develop clear, trackable, and
practical solutions while communicat-
ing trends and needs to world leaders.
Working together while respecting the
diversity of people and opinions and
the need for social justice around the
world, we can make great progress for
the sake of humanity and the planet on
which we depend.
Spanish, Portuguese, and French
versions of this article can be found
in file S1.
Peter Frumhoff and Doug Boucher
of the Union of Concerned Scientists,
as well as the following individuals,
provided thoughtful discussions,
comments, or data for this paper: Stuart
Pimm, David Johns, David Pengelley,
Guillaume Chapron, Steve Montzka,
Robert Diaz, Drik Zeller, Gary
Gibson, Leslie Green, Nick Houtman,
Peter Stoel, Karen Josephson, Robin
Comforto, Terralyn Vandetta, Luke
Painter, Rodolfo Dirzo, Guy Peer, Peter
Haswell, and Robert Johnson.
Supplemental material
Supplementary data are available at
BIOSCI online including supplemental
file 1 and supplemental file 2 (full list
of all 15,364 signatories).
References cited
Crist E, Mora C, Engelman R. 2017. The interac-
tion of human population, food production,
and biodiversity protection. Science 356:
Hansen J, et al. 2013. Assessing “dangerous
climate change”: Required reduction of
carbon emissions to protect young people,
future generations and nature. PLOS ONE
8 (art. e81648).
Keenan, RJ, Reams GA, Achard F, de Freitas JV,
Grainger A, Lindquist E. 2015. Dynamics
of global forest area: Results from the FAO
Global Forest Resources Assessment 2015.
Forest Ecology and Management 352: 9–20.
Ripple WJ, Smith P, Haberl H, Montzka SA,
McAlpine C, Boucher DH. 2014. Ruminants,
climate change and climate policy. Nature
Climate Change 4: 2–5. doi:10.1038/
William J. Ripple (,
Christopher Wolf, and Thomas M. Newsome
are affiliated with the Global Trophic Cascades
Program in the Department of Forest Ecosystems
and Society at Oregon State University, in
Corvallis. TMN is also affiliated with the Centre
for Integrative Ecology at Deakin University, in
Geelong, Australia, and the School of Life and
Environmental Sciences at The University of
Sydney, Australia. Mauro Galetti is affiliated
with the Instituto de Biociências, Universidade
Estadual Paulista, Departamento de Ecologia,
in São Paulo, Brazil. Mohammed Alamgir
is affiliated with the Institute of Forestry and
Environmental Sciences at the University of
Chittagong, in Bangladesh. Eileen Crist is
affiliated with the Department of Science and
Technology in Society at Virginia Tech, in
Blacksburg. Mahmoud I. Mahmoud is affiliated
with the ICT/Geographic Information Systems
Unit of the National Oil Spill Detection and
Response Agency (NOSDRA), in Abuja, Nigeria.
William F. Laurance is affiliated with the Centre
for Tropical Environmental and Sustainability
Science and the College of Science and
Engineering at James Cook University, in Cairns,
Queensland, Australia.
... Several empirical pieces of evidence reveal rainfall variability and temperature rise impact agricultural productivity, water availability, and biodiversity (Parry et al. 2009;Ripple et al. 2017;IPCC 2021). Rural livelihoods in Ethiopia, such as agriculture, pastoralism, and agropastoralism, are extremely sensitive to climate variability and change due to their close ties to the natural environment. ...
Full-text available
This study aims to investigate spatiotemporal variability, trends, and anomaly in rainfall and temperature in the Sidama region, Ethiopia. The TerraClimate gridded dataset on a monthly time scale for 30 years (1991–2020) with a horizontal resolution of approximately 4 km was used for the study. Trends in annual and seasonal rainfall and temperature were assessed using a nonparametric test (Mann-Kendal test) and Sen’s slope, to test the statistical significance and magnitude of trends (increase/decrease), respectively. Our findings revealed that annual rainfall, summer ( Hawado ), and spring ( Badhessa ) rainfall have shown an increasing trend in most parts of the region, except for its northwest parts. We found a low annual rainfall variability (CV < 13%) over the southeastern and northwestern parts of the region. Rainfall variability revealed the difference in both time and space across the region. Six drought years (1999, 2001, 2002, 2003, 2012, and 2019) with different magnitudes were identified across the region. Annual average maximum (up to 0.4°C decade –1 ) and minimum (up to 0.25°C decade –1 ) temperatures revealed significantly increasing trends across the region. The standardized anomaly in the mean annual temperature indicated that the years in the recent decade (2011–2020) are getting warmer compared to the past two decades (1991–2010) due to climate change and other local and regional factors that cause weather extremes in the region. The results of this study for rainfall contradict the other studies in the rift valley part of the region. Therefore, we suggest the design and implementation of locally driven climate change adaptation strategies so that there is high rainfall and temperature variability across the region and between seasons.
... We are amid a planetary emergency, largely pushed by extensive forest loss, which causes a myriad of cascading effects on biodiversity, including our own species (Ripple et al., 2017;Rockström et al., 2009). Forest loss is largely driven by agriculture worldwide, especially by large-scale (commercial) agriculture (FAO, 2020). ...
Forest's recovery potential in human-modified landscapes is increasingly threatened by agricultural activities that disrupt critical sources of forest regeneration, such as the seed rain. Slash-and-burn agriculture is a good example. By slashing and burning the vegetation, this farming method can promote seed source and seed dispersal limitation, but this hypothesis remains poorly tested. Here, we sampled the seed rain during a complete year in nine plots exposed to slash-and-burn agriculture (i.e., burned plots) and in forest stands (control plots) in the Caatinga biome-a species-rich tropical dry forest endemic to Brazil that is increasingly threatened by slash-and-burn agriculture. We compared seed density, seed species diversity, and the taxonomic and functional composition of seed assemblages between burned and control plots. As expected, seed density was 15 times lower in burned plots than in control plots. Species diversity was also lower in burned plots, but only when considering the number of rare species. However, burned plots showed a higher β-diversity of rare species than forest plots, mainly caused by species replacement (i.e. species turnover) from plot to plot. Burned plots also showed 30% more species with dry fruits and abiotic dispersal than control plots, but this difference was not statistically significant. Taken together, our findings highlight the low tolerance of the seed rain to this dominant agricultural practice in tropical dry forests. This is likely related to the lack of seed sources and seed dispersers in burned plots. Therefore, increasing the availability of seed sources and ecological connectivity in the surrounding landscape are critical management strategies for enhancing seed dispersal and forest recovery in forest areas exposed to this farming method.
Given the urgent need for change that has become even more evident during the pandemic, it seems fitting to critically reflect on our responsibilities as scholars, educators and colleagues, individually and as members of a purposeful, supportive community, in facilitating a more sustainable world. We share a roundtable discussion that was part of the 13th Spanish CSEAR conference in hopes that the conversation will continue within the community regarding some of the perceived roles, opportunities and responsibilities post-pandemic. The perspectives shared are from a group of scholars at different stages in their careers, who have different profiles, and see their responsibilities differently. These individual and collective perspectives address personal and professional aspirations, the focus and purpose of research, and the role of CSEAR as we move into the future. Hopefully by sharing perspectives from different vantage points ranging from the beginning to the end of the ‘academic life cycle’, we can stimulate and facilitate meaningful dialogue and debate within, and about the future of, our community leading to a more resilient, active, caring, supportive, inspiring, encouraging and helpful environment and more effectively further the transition to a more sustainable world.
The purpose of this paper is to explore the role of knowledge-based dynamic capabilities in national innovation systems in the achievement of sustainable development goals, employing an empirical approach in the context of the unprecedented COVID-19 crisis. Based on data from 130 sample countries, we analyzed the impact of knowledge-based dynamic capabilities on the achievement of sustainable development goals using PLS-SEM. In particular, we considered the differences in the impact of knowledge-based dynamic capabilities on the achievement of sustainable development goals at different stages of economic development. The results show that knowledge-based dynamic capabilities have a positive impact on the achievement of sustainable development goals, while their compositional dimensions have a dual impact, both direct and indirect. In addition, knowledge-based dynamic capabilities have different impacts on the achievement of sustainable development goals at different stages of economic development. This indicates that a country's economic development level will affect the relationship between knowledge-based dynamic capabilities and the achievement of sustainable development goals. However, it also means that there is a more complex relationship between these capabilities and the achievement of the goals. This study offers a new perspective for sustainable development research, adds new insights to the theory of linking knowledge-based dynamic capabilities to the achievement of sustainable development goals, and provides a measurement standard for the impact of those capabilities on the goals.
Public and private sector financing is essential in the movement of capital to achieve all seventeen Sustainable Development Goals (SDGs) by the United Nations members by 2030. Foreign direct investment (FDI) is considered the primary source of external financing in the private sector. FDI accelerates the economic growth of any country by mobilising capital, increasing labour productivity, technological advancements, etc. The present paper aims to study the potential effect of FDI on Sustainable Development in Eurasian countries. Our research considers a sample of 78 Eurasian countries, further distinguished by their income classes. Considering the neoclassical theory of FDI, suggests that FDI will lead to economic growth in the recipient country through flows of capital injections, higher labour growth, productivity and technological advancement. In this study, the variables related to government expenditures are considered to predict a positive association with the SDG index variable. We applied a fixed effects regression model to investigate the relation between FDI and SDG index. Our findings reveal that there is a positive and significant effect of FDI on the SDG index. Furthermore, our results also indicate that the role of FDI is more decisive and fundamental the lower the income class of the countries. Our research contributes to the current literature on Sustainable Development. We believe that our research paper will serve as a base for policy recommendations and future research studies on the influence of FDI on sustainable development for Eurasian countries.
The global problem of biological invasions will continue escalating, given inadequate biosecurity worldwide. Developing stringent biosecurity is hindered by the lacking essential information on the global flows of alien species, especially alien species accidentally transported and neglected by biosecurity due to inapparent economic significance. We provide evidence and new perspectives on the temporal, geographical, taxonomic, and transport sub-pathway dimensions of the global flows of neglected alien species, using alien amphibians and reptiles (“herpetofauna”) accidentally transported to New Zealand as a case study (2610 records from 1929 to 2021). We decomposed and forecasted the alien herpetofauna transport frequency using locally-weighted smoothing and dynamic regression modelling. We explored geographical patterns of the alien herpetofauna origins and destinations, and explored temporal trends in species diversity. Finally, we analysed a species×transport sub-pathway network to elucidate the diversity of sub-pathways used by alien herpetofauna. Alien herpetofauna transport frequency is generally increasing, with fluctuations coinciding with changes in biosecurity and economic expansion and recessions. The most recent decline was during the COVID-19 recession, but we forecast transport to recover. Two hundred and forty-three alien herpetofauna worldwide arrived at ports of entry across New Zealand. Alien herpetofauna were accidentally transported through 13 sub-pathways, primarily as stowaways in 'personal effects and household goods', and in 'machinery, vehicles, and equipment'. Our study illuminates that neglected alien species' transport frequency, spatial extent of origins and destinations, species diversity, and accidental transport sub-pathways are hugely underestimated and dynamic. These crucial oversights in the global flows of alien species significantly impede biosecurity worldwide.
Full-text available
Hunting has been crucial in early human evolution. Some San (Bushmen) of southern Africa still practice their indigenous hunting. The use of poisons is one remarkable aspect of their bow-and-arrow hunting but the sources, taxonomic identifications of species used, and recipes , are not well documented. This study reports on fieldwork to investigate recent indigenous hunting practices of G/ui and G//ana San communities in the Central Kalahari Game Reserve (CKGR), Botswana. Here we discuss their use of spider poison. The hunters use the contents of the opisthosoma ('abdomen') of a spider as sole ingredient of the arrow poison and discard the prosoma that contains the venom-glands. Using taxonomic keys, we identified the spider as the garden orb-web spider Argiope australis (Walckenaer 1805) (Araneidae). The hunters' choice of this species is remarkable given the scientific perception that A. australis is of little medical importance. The species choice raises questions about how the spider fluids could kill game, particularly when the prosoma, which contains the venom glands, is not used. Possibilities include trauma, as a source of pathogens, or abdomen containing toxins. Based on characteristics of Argiope Audouin 1826, we hypothesize that the choice of this species for arrow poisons might have evolved from the recognition of aposematic signalling or spiritual symbolism. Indigenous knowledge (IK) is an important source for advances in biotechnology but is in decline worldwide. The study contributes to the documentation of the San people, and their ancient IK, which is threatened by marginali-zation, political pressures, and climate change. PLOS ONE PLOS ONE |
Full-text available
Research suggests that the scale of human population and the current pace of its growth contribute substantially to the loss of biological diversity. Although technological change and unequal consumption inextricably mingle with demographic impacts on the environment, the needs of all human beings—especially for food—imply that projected population growth will undermine protection of the natural world. Numerous solutions have been proposed to boost food production while protecting biodiversity, but alone these proposals are unlikely to staunch biodiversity loss. An important approach to sustaining biodiversity and human well-being is through actions that can slow and eventually reverse population growth: investing in universal access to reproductive health services and contraceptive technologies, advancing women’s education, and achieving gender equality.
Full-text available
Greenhouse gas emissions from ruminant meat production are significant. Reductions in global ruminant numbers could make a substantial contribution to climate change mitigation goals and yield important social and environmental co-benefits. A lthough a main focus of climate policy has been to reduce fossil fuel consumption, large cuts in CO 2 emissions alone will not abate climate change. At present non-CO 2 greenhouse gases contribute about a third of total anthropogenic CO 2 equivalent (CO 2 e) emissions and 35–45% of climate forcing (the change in radiant energy retained by Earth owing to emissions of long-lived greenhouse gases) resulting from those emissions 1 (Fig.1a). Only with large simultaneous reductions in CO 2 and non-CO 2 emissions will direct radiative forcing be reduced during this century (Fig.1b). Methane (CH 4) is the most abundant non-CO 2 greenhouse gas and because it has a much shorter atmospheric lifetime (~9years) than CO 2 it holds the potential for more rapid reductions in radiative forcing than would be possible by controlling emissions of CO 2 alone. There are several important anthropogenic sources of CH 4 : ruminants, the fossil fuel industry, landfills, biomass burning and rice production (Fig.1c). We focus on ruminants for four reasons. First, ruminant production is the largest source of anthropogenic CH 4 emissions (Fig.1c) and globally occupies more area than any other land use. Second, the relative neglect of this greenhouse gas source suggests that awareness of its importance is inappropriately low. Third, reductions in ruminant numbers and ruminant meat production would simultaneously benefit global food security, human health and environmental conservation. Finally, with political will, decreases in worldwide ruminant populations could potentially be accomplished quickly and relatively inexpensively. Ruminant animals consist of both native and domesticated herbivores that consume plants and digest them through the process of enteric fermentation in a multichambered stomach. Methane is produced as a by-product of microbial digestive processes in the rumen. Non-ruminants or 'monogastric' animals such as pigs and poultry have a single-chambered stomach to digest food, and their methane emissions are negligible in comparison. There are no available estimates of the number of wild ruminants, but it is likely that domestic ruminants greatly outnumber the wild population, with a reported 3.6billion domestic ruminants on Earth in 2011 (1.4 billon cattle, 1.1 billion sheep, 0.9 billion goats and 0.2 billon buffalo) 2 . On average, 25million domestic ruminants have been added to the planet each year (2million per month) 2 over the past 50years (Fig.1d). Worldwide, the livestock sector is responsible for approximately 14.5% of all anthropogenic greenhouse gas emissions 3 (7.1of 49GtCO 2 eyr –1). Approximately 44% (3.1GtCO 2 eyr –1) of the livestock sector's emissions are in the form of CH 4 from enteric fermentation, manure and rice feed, with the remaining portions almost equally shared between CO 2 (27%, 2GtCO 2 eyr –1) from land-use change and fossil fuel use, and nitrous oxide (N 2 O) (29%, 2GtCO 2 eyr –1) from fertilizer applied to feed-crop fields and manure 3 . Ruminants contribute significantly more (5.7GtCO 2 eyr –1) to greenhouse gas emissions than monogastric livestock (1.4GtCO 2 eyr –1), and emissions due to cattle (4.6GtCO 2 eyr –1) are substantially higher than those from buffalo (0.6GtCO 2 eyr –1) or sheep and goats (0.5GtCO 2 eyr –1) 3 . Globally, ruminants contribute 11.6% and cattle 9.4% of all greenhouse gas emissions from anthropogenic sources. The total area dedicated to grazing encompasses 26% of the terrestrial surface of the planet 4 . Livestock production accounts for 70% of global agricultural land and the area dedicated to feed-crop production represents 33% of total arable land 4 . The feeding of crops to livestock is in direct competition with producing crops for human consumption (food security) and climate mitigation (bioenergy production or carbon sequestration) 5 . Deforestation has been responsible for a significant proportion of global greenhouse gas emissions from the livestock sector and takes place mostly in tropical areas, where expansion of pasture and arable land for animal feed crops occurs primarily at the expense of native forests 4,6 . Lower demand for ruminant meat would therefore reduce a significant driver of tropical deforestation and associated burning and black carbon emissions. The accompanying reduction in grazing intensity could also allow regrowth of forests and other natural vegetation, resulting in additional carbon sequestration in both biomass and soils with beneficial climate feedbacks 5,6 . Lower global ruminant numbers would have simultaneous benefits for other systems and processes. For example, in some grassland and savannah ecosystems, domestic ruminant grazing contributes to land degradation through desertification and reduced soil organic carbon 5 . Ruminant agriculture can also have negative impacts on water quality and availability, hydrology and riparian ecosystems 4,7 . Ruminant production can erode biodiversity through a wide range of processes such as forest loss and degradation, land-use intensification, exotic plant invasions, soil erosion, persecution of large predators and competition with wildlife for resources 4–7 . Ruminant production also has implications for food security and human
Full-text available
We assess climate impacts of global warming using ongoing observations and paleoclimate data. We use Earth's measured energy imbalance, paleoclimate data, and simple representations of the global carbon cycle and temperature to define emission reductions needed to stabilize climate and avoid potentially disastrous impacts on today's young people, future generations, and nature. A cumulative industrial-era limit of ∼500 GtC fossil fuel emissions and 100 GtC storage in the biosphere and soil would keep climate close to the Holocene range to which humanity and other species are adapted. Cumulative emissions of ∼1000 GtC, sometimes associated with 2°C global warming, would spur "slow" feedbacks and eventual warming of 3-4°C with disastrous consequences. Rapid emissions reduction is required to restore Earth's energy balance and avoid ocean heat uptake that would practically guarantee irreversible effects. Continuation of high fossil fuel emissions, given current knowledge of the consequences, would be an act of extraordinary witting intergenerational injustice. Responsible policymaking requires a rising price on carbon emissions that would preclude emissions from most remaining coal and unconventional fossil fuels and phase down emissions from conventional fossil fuels.
The area of land covered by forest and trees is an important indicator of environmental condition. This study presents and analyses results from the Global Forest Resources Assessment 2015 (FRA 2015) of the Food and Agriculture Organization of the United Nations. FRA 2015 was based on responses to surveys by individual countries using a common reporting framework, agreed definitions and reporting standards. Results indicated that total forest area declined by 3%, from 4128 M ha in 1990 to 3999 M ha in 2015. The annual rate of net forest loss halved from 7.3 M ha y−1 in the 1990s to 3.3 M ha y−1 between 2010 and 2015. Natural forest area declined from 3961 M ha to 3721 M ha between 1990 and 2015, while planted forest (including rubber plantations) increased from 168 M ha to 278 M ha. From 2010 to 2015, tropical forest area declined at a rate of 5.5 M ha y−1 – only 58% of the rate in the 1990s – while temperate forest area expanded at a rate of 2.2 M ha y−1. Boreal and sub-tropical forest areas showed little net change. Forest area expanded in Europe, North America, the Caribbean, East Asia, and Western-Central Asia, but declined in Central America, South America, South and Southeast Asia and all three regions in Africa. Analysis indicates that, between 1990 and 2015, 13 tropical countries may have either passed through their forest transitions from net forest loss to net forest expansion, or continued along the path of forest expansion that follows these transitions. Comparing FRA 2015 statistics with the findings of global and pan-tropical remote-sensing forest area surveys was challenging, due to differences in assessment periods, the definitions of forest and remote sensing methods. More investment in national and global forest monitoring is needed to provide better support for international initiatives to increase sustainable forest management and reduce forest loss, particularly in tropical countries.
Ruminants, climate change and climate policy
  • W J Ripple
  • P Smith
  • H Haberl
  • S A Montzka
  • C Mcalpine
  • D H Boucher
Ripple WJ, Smith P, Haberl H, Montzka SA, McAlpine C, Boucher DH. 2014. Ruminants, climate change and climate policy. Nature Climate Change 4: 2-5. doi:10.1038/ nclimate2081
Newsome are affiliated with the Global Trophic Cascades
  • William J Ripple
William J. Ripple (, Christopher Wolf, and Thomas M. Newsome are affiliated with the Global Trophic Cascades