TOMORROWS

17 CHANGE, UNCERTAINTY AND LACK OF KNOWLEDGE:
BRAZILIAN BIODIVERSITY IN THE 21ST CENTURY

Scientists have no crystal balls to foresee the future, but even so they can make predictions or projections. Scientific forecasts about biodiversity may basically be produced in two ways. It is possible to examine the relationship between various factors (including climate and solar radiation) and alterations to diversity in the past, and to project this relationship forward to future conditions of these factors. Alternatively, making assumptions about how certain factors cause modifications to biodiversity, we can construct a model of cause-and-effect relationships, with which we can predict future alterations.

Before considering the future of biological diversity, let us think about climate. The quality of weather forecast services improved considerably during the 20th century. Predictions of up to five days are now quite reliable. On the other hand, projecting climate change in the coming decades is much more uncertain, and scientists are producing different models (or scenarios) to explore possible alternatives, without assuring that any particular one is more “truthful” or reliable than the others.

If there is uncertainty about the future of the planet’s climate, it is much greater with regard to even more complex phenomena, such as those concerning biological diversity. Therefore we have to understand the reasons for uncertainty in order to know whether it can be overcome or circumvented.

The first issue we are faced with is lack of knowledge. Brazil is one of the planet’s highest-ranking countries in biodiversity; as a result, our knowledge about how many and which species live here is manifestly incomplete. [1] This ignorance is especially serious with regard to invertebrate animals and microorganisms. However, we do not even know all the Brazilian species of the most studied organisms, such as larger animals (mammals and birds, for example) or trees. The lack of knowledge is even more severe with regard to the geographical distribution of species. For the overwhelming majority of species, we lack complete distribution maps, not least because there are vast areas of Brazil in which no biological studies or surveys have been carried out, especially in the Central and Northern regions.

Few people realize that extinction most strongly affects a silent multitude of small, unobtrusive organisms, which live in restricted environments. The greatest difficulty in evaluating the vulnerability of this practically countless number of species is that they are disappearing before we have even discovered them, much less evaluate their inclusion on lists of endangered species.

Outra dimensão Another dimension of Brazilian biodiversity, in which our ignorance is less obvious but perhaps even more serious, is the way species organize themselves in ecosystems. This organization needs to be understood in order to enable us to grasp Brazil’s current environmental dilemmas and make critical choices for the future. Without knowing which animals visit and pollinate plants in cultivated fields, for example, we will not be able to understand and predict the future course of the crisis of pollinators, which is already compromising many agricultural crops in Brazil and around the world.[2]

In addition to the problems of lack of knowledge, we are also faced with uncertainties in projecting past trends into the future. We know less about the past of Brazilian biodiversity than its present condition – this applies both to remote time (including major changes over the course of geological eras) and to recent times (in which alterations have been caused by growing human occupation and modification). Obviously, it is hard to project trends into the future based on a little-understood past. Furthermore, all projections presuppose that future effects will be similar to those of the past, and there are good reasons to question whether this will hold for biodiversity.

Predictions produced based on cause-and-effect models depend on identifying the most important factors in a given process and then ascertaining how they act in combination. Thus, for example, in climate change forecasts for the coming decades, it is likely that alterations of rain and drought regimes will affect Brazilian ecosystems more strongly than changes in temperature itself –bearing in mind, however, that temperature and precipitation or humidity do not affect living organisms independently.

Such uncertainties should be included in scientific models, in order for all the plausible options to be evaluated in line with our current knowledge. We should also add confidence intervals to each forecast, rather than presenting supposedly exact projections. These intervals do not indicate that scientists are incompetent. On the contrary, they are the appropriate way to cope with the uncertainty inherent to systems as complex as environmental ones, based on incomplete knowledge.

Given these considerations about climate issues, how should we approach the future of biodiversity? The official Brazilian list of endangered species contains 464 species of land vertebrates, as well as eight species considered extinct in Brazil.3 For fish and invertebrates, this list is much more incomplete, because there are many groups for which the risk of extinction cannot even be evaluated, given the lack of specific knowledge. The Brazilian list of plants now includes 2,113 endangered species.4 Some of these species only survive in very small populations and depend on very particular environmental conditions in sites that are also disappearing. Thus, it seems inevitable that some of the species on these official lists will indeed vanish in the not-too-distant future.

We cannot say that each species has a unique function in its ecosystem. The extinction of a given species of bromeliad or bird, for example, may not have obvious consequences for the functioning of the ecosystems in which they live. In any case, however, it makes the world a poorer place to live in, even for the vast majority of people who live in large cities and have practically no direct contact with well-conserved nature.

The majority of species are not capable of migrating long distances, except if there are stepping stones, and this requires more or less continuous favorable environments. Cultivated fields, vast areas of pastureland and cities increasingly restrict natural ecosystems to small, isolated areas.

Initiatives to reverse imminent extinctions have been successful in some cases. The best known example in Brazil is perhaps that of the golden lion tamarin, which although still endangered, left the “critically endangered” status in 2003, and whose numbers continue to increase. [5] The recovery of a single species requires huge efforts, including human and material resources, which cannot be replicated for every one of the thousands of species listed as threatened. However, few people realize that extinction most strongly affects a silent multitude of small, unobtrusive organisms, which live in restricted environments. The greatest difficulty in evaluating the vulnerability of this practically countless number of species is that they are disappearing before we have even discovered them, much less evaluate their inclusion in lists of endangered species.

In addition to our concerns about the extinction of certain species, we should expect other alterations in Brazilian biodiversity, which one way or another will affect the majority of living organisms. Climate modifications will force species to shift to regions in which the new conditions are more favorable to them. This displacement may involve anything from small distances between adjacent habitats or upwards on mountain slopes, to migrations over longer distances.

However, things are unlikely to take place in a simple, easy way: the majority of species are not capable of migrating over long distances, except if there are stepping stones, and this requires more or less continuous favorable environments. Cultivated fields, vast areas of pastureland and cities increasingly restrict natural ecosystems to small, isolated areas. Moreover, new regions, which become favorable under an altered climate, are likely to be occupied by homes or crops, preventing or hindering their allocation for biodiversity protection and, moreover, requiring an ecological restoration process.

One foreseeable consequence of species displacements induced by climate change, or directly entailed by human activities, is the expansion of some species that are ecologically aggressive or highly favored by environmental disturbances. Besides altering important processes in ecosystems, the establishment of exotic species in new regions makes the world more ecologically uniform, in a process called biotic homogenization.[6]

As already mentioned, the disappearance of interesting species impoverishes the world. However, disruption of ecosystem functioning has broader and more serious consequences, as it affects environmental integrity and the quality of human life itself in many ways. The functioning of ecosystems and many of the services they provide for human wellbeing largely depends on the enormous variety of small organisms, such as insects, algae and microorganisms, which exist in all natural and modified environments. For this reason, it is necessary to invest in the integrity of biodiversity, not only by preserving ecosystems in more natural conditions in protected areas, but also by paying attention to the diversity and ecological organization of the organisms that live in agricultural and urban landscapes.

One example already cited is the importance of native animal species as pollination agents for crops and orchards. Accordingly, the reduction of bee populations is causing concern, as it is harming an ecosystem service of great agricultural importance, which is difficult and expensive to replace.

An even greater complicating factor involves the propagation and successive effects of changes to ecosystems, which may interfere with different functions and generate consequences in other areas even on very large scales. Thus, we do not yet know the entire effects of deforestation that is accelerating yet again in the southern and southeastern Amazon. In addition to disrupting ecosystems in the region itself, it is increasingly evident that this deforestation, combined with the extensive agricultural occupation of the Cerrado region, has contributed to raising temperatures and reducing rainfall in the Southeast region. Among many other consequences, this is simultaneously harming human health, the production of hydroelectric power, river shipment and agricultural production.

The functioning of ecosystems and many of the services they provide for human wellbeing largely depends on the enormous variety of small organisms, such as insects, algae or micro-organisms, which exist in all natural and modified environments. For this reason, it is necessary to invest in the integrity of biodiversity.

Finally, one last factor further increases uncertainty regarding the future of Brazilian biodiversity. This one, however, also allows for some cautious optimism. Brazil is one of the few countries to still have a wide range of options as to its environmental future, including its biological diversity. This is due to a unique combination of extensive spaces, enormous native biodiversity and a still fairly sparse human population in much of its territory (although it is critically dense in continuously expanding urban areas, especially in the Atlantic Forest and Cerrado regions).

Everything depends on the government and citizens realizing that quality of life, well-being, sustainable production and a solid economy are ultimately inseparable from the integrity and proper functioning of ecosystems. Life will be more secure, healthier and buffered from extreme conditions in landscapes that reconcile agricultural production and human habitation with the preservation of ecosystems. We can only gain by enabling the benefits of preservation to encompass all human requirements and activities.

However, the time to take decisions is fast running out – and, given the uncertainties involved, we should not count on advance notice of the moment when our opportunity for choice expires.

Previous chapter Oceans, the new human frontier
You are here: Tomorrows
Next chapter The shape of the future